UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): July 910, 2026 (July 6, 2026)

PLUM ACQUISITION CORP. IV

(Exact name of registrant as specified in its charter)

Cayman Islands		001-42472		98-1795710
(State or other jurisdiction of incorporation or organization)		(Commission File Number)		(I.R.S. Employer Identification Number)

2021 Fillmore St. #2089

San Francisco, California

94115

(Address of principal executive offices)

(Zip Code)

Registrant’s telephone number, including area code: (929) 529-7125

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation to the registrant under any of the following provisions:

☐☒ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☒☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Units, each consisting of one Class A ordinary share, par value $0.0001 per share, and one-half of one redeemable warrant	PLMKU	Nasdaq Global Market
Class A ordinary shares, par value $0.0001 per share, included as part of the units	PLMK	Nasdaq Global Market
Warrants included as part of the units, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50	PLMKW	Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 or Rule 12b-2 of the Securities Exchange Act of 1934.

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 81.01. ~~Other~~Entry ~~Events~~into a Material Definitive Agreement.

~~Announcement~~As previously disclosed, Plum Acquisition Corp. IV, a Cayman Islands exempted company (which will transfer by way of ~~Estimated~~continuation ~~Redemption~~from ~~Price~~ the Cayman Islands to the State of Delaware and domesticate as a Delaware corporation prior to the closing of the Transactions (as defined below)) (“Plum IV”), Plum IV Merger Sub, Inc., a Delaware corporation and a direct wholly owned subsidiary of Plum IV (“Merger Sub”), and Controlled Thermal Resources Holdings Inc., a Delaware corporation (the “Company”) entered into a Business Combination Agreement (as amended on May 15, 2026, the “Business Combination”), pursuant to which, among other things and subject to the terms and conditions contained therein, Merger Sub will merge with and into the Company, with the Company continuing as the surviving company.

AsOn ~~previously~~July ~~disclosed~~6, 2026, Plum ~~Acquisition Corp.~~ IV (, the “Company”) ~~will~~and ~~hold~~Merger Sub anentered ~~extraordinary~~into ~~general~~a ~~meeting~~second ofamendment ~~its~~to ~~shareholders~~the Business Combination Agreement (the “~~Shareholder~~Second ~~Meeting~~BCA Amendment”~~) on~~ ~~July~~and 10the Business Combination Agreement, ~~2026~~as atamended ~~9:00~~by ~~a.m.~~the Second BCA Amendment, ~~Eastern~~the ~~Time~~“Amended BCA”), atwhich amends the ~~offices~~Business Combination ofAgreement ~~Greenberg Traurig~~to, ~~P.A.,~~among ~~located~~other atthings, ~~777~~(i) S.reduce ~~Flagler~~the ~~Drive,~~aggregate ~~Suite~~number ~~300~~of ~~East, West~~potential ~~Palm~~earnout ~~Beach,~~shares FLissuable ~~33401,~~to ~~where~~the Company’s shareholders ~~will~~following bethe ~~asked,~~closing ~~among~~from ~~other things~~100,000,000 to ~~amend~~70,000,000, with each of the ~~Company’s~~eight ~~amended~~earnout ~~and~~tranches ~~restated~~reduced ~~memorandum~~proportionally from ~~and~~12,500,000 ~~articles~~to of8,750,000 ~~association~~shares; to(ii) extend the date ~~(the “Termination Date”)~~ by which the ~~Company~~parties ~~has~~are required to ~~consummate~~make aany ~~business combination~~filings ~~from~~or ~~July~~applications ~~16,~~required ~~2026~~under antitrust tolaws ~~January~~with ~~16,~~respect ~~2027~~to (the ~~“Articles~~transactions ~~Extension~~contemplated ~~Date”)~~by ~~and~~the toAmended ~~allow~~BCA (the ~~Company,~~“Transactions”) ~~without another~~from ~~shareholder~~July ~~vote~~31, 2026 to ~~elect~~September to30, ~~extend~~2026; ~~the~~(iii) ~~Termination~~increase ~~Date~~the tomaximum ~~consummate~~number aof ~~business~~shares ~~combination~~issuable onto aPlum ~~monthly~~Partners ~~basis~~IV, ~~for~~LLC upas toreimbursement ~~six~~for founder ~~times~~shares byissued anto ~~additional~~Plum ~~one~~IV ~~month~~shareholders, ~~each~~or ~~time~~issuable ~~after~~to ~~the~~Plum ~~Articles~~IV ~~Extension Date~~shareholders, bywho ~~resolution~~agree ofnot ~~the~~to ~~Company’s~~redeem ~~board~~their ofPlum ~~directors if~~IV ~~requested~~shares byfrom ~~Plum~~2,000,000 to ~~Partners IV~~3,000,000; ~~LLC~~(iv) ~~and~~extend ~~upon~~the ~~five~~date ~~days’~~by ~~advance~~which ~~notice~~the ~~prior~~closing tomust ~~the~~occur ~~applicable~~from ~~Termination~~December ~~Date~~31, ~~until~~2026 ~~July~~to 16April 30, 2027,; or(v) areduce ~~total~~the ofvaluation used up to ~~twelve~~calculate ~~months~~the ~~after~~merger ~~the~~consideration ~~Termination~~from ~~Date~~$4,500,000,000 ~~unless~~to ~~the~~$3,150,000,000; ~~closing~~and of(vi) aextend ~~business~~the ~~combination~~deadlines ~~shall~~by ~~have~~which ~~occurred~~the ~~prior~~Company is required to ~~such~~deliver ~~date~~certain (material consents to the ~~“Extension~~dates ~~Amendment~~listed ~~Proposal”~~on Schedule 8.01(m) to the Amended BCA.

InThe ~~connection~~foregoing ~~with~~description of the ~~Extension~~Second ~~Amendment~~BCA ~~Proposal, shareholders may elect to redeem their public shares (an “Election”)~~Amendment atdoes anot ~~per-share~~purport ~~price, payable in cash, equal~~ to ~~the~~be ~~aggregate~~complete ~~amount~~and ~~then~~is onqualified ~~deposit~~ in ~~the~~its ~~trust~~entirety ~~account~~by ~~established~~reference into ~~connection with~~ the ~~Company’s~~full ~~initial~~text ~~public offering (the “Trust Account”), including interest earned on the Trust Account, divided by the number~~ of ~~then outstanding public shares. Based upon~~ the ~~amount~~Second inBCA ~~the Trust Account as of July 9~~Amendment, ~~2026,~~a ~~which~~copy ~~was approximately~~of ~~$184,528,681.34, the preliminary estimated per-share price at~~ which ~~public~~is ~~shares~~filed ~~will~~as beExhibit ~~redeemed in connection with an Election will be approximately $~~10.~~6973~~1 atto ~~the~~this ~~time~~Current ofReport ~~the Shareholder Meeting. The closing price of the public shares~~ on ~~the~~Form ~~Nasdaq~~8-K ~~Stock~~(“Current ~~Market~~Report”), ~~LLC on~~and ~~July~~incorporated 9,herein ~~2026,~~by ~~was $10~~reference.77. The Company cannot assure shareholders that they will be able to sell their public shares in the open market, even if the market price per share is higher than the redemption price stated above, as there may not be sufficient liquidity in the Company’s securities when such shareholders wish to sell their shares.

~~Shareholders~~Additional ~~who wish to withdraw their previously submitted redemption requests may continue to do so prior to the Shareholder Meeting~~Information byand ~~requesting~~Where ~~that the transfer agent return such public shares prior~~ to ~~9:00~~Find ~~a.m., Eastern Time, on July 10, 2026, or such later time as may be determined by the Company.~~ It

In connection with the ~~Cautionary~~Transactions, ~~Note~~Plum ~~Regarding~~IV ~~Forward~~and the Company intend to file with the SEC a registration statement on Form S-~~Looking~~4 ~~Statements~~(the “Registration Statement”), which will include a preliminary proxy statement of Plum IV as well as a preliminary prospectus relating to the offer of securities to be issued to the stockholders of the Company (the “Proxy Statement/Prospectus”). After the Registration Statement is declared effective, a definitive proxy statement and other relevant documents will be mailed to shareholders of Plum IV as of the record date to be established for voting on the Transactions and other matters as described in the Proxy Statement/Prospectus. Plum IV will also file other documents regarding the Transactions with the SEC. This Current Report does not contain all of the information that should be considered concerning the Transactions and is not intended to form the basis of any investment decision or any other decision in respect of the Transactions. BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, SHAREHOLDERS OF PLUM IV AND OTHER INTERESTED PARTIES ARE URGED TO READ, WHEN AVAILABLE, THE PRELIMINARY PROXY STATEMENT/PROSPECTUS, AND AMENDMENTS THERETO, AND THE DEFINITIVE PROXY STATEMENT/PROSPECTUS AND ALL OTHER RELEVANT DOCUMENTS FILED OR THAT WILL BE FILED WITH THE SEC IN CONNECTION WITH PLUM IV’S SOLICITATION OF PROXIES FOR THE EXTRAORDINARY GENERAL MEETING OF ITS SHAREHOLDERS TO BE HELD TO APPROVE THE TRANSACTIONS AND OTHER MATTERS AS DESCRIBED IN THE PROXY STATEMENT/PROSPECTUS BECAUSE THESE DOCUMENTS WILL CONTAIN IMPORTANT INFORMATION ABOUT PLUM IV, the Company AND THE TRANSACTIONS. Investors and security holders will also be able to obtain copies of the Registration Statement and the Proxy Statement/Prospectus and all other documents filed or to be filed with the SEC by Plum IV, without charge, once available, on the SEC’s website at www.sec.gov or by directing a request to: Plum Acquisition Corp. IV, 2021 Fillmore St., #2089, San Francisco, California 94115, Attention: Kanishka Roy, or by email at [email protected].

This Current Report on Form 8-K (“Current Report”) contains statements that are forward-looking and as such are not historical facts. This includes, without limitation, statements regarding the estimated redemption price per share at the Shareholder Meeting. These statements constitute projections, forecasts and forward-looking statements, and are not guarantees of performance. They involve known and unknown risks, uncertainties, assumptions and other factors that may cause the actual results, performance or achievements of the Company to be materially different from any future results, performance or achievements expressed or implied by these statements. Such statements can be identified by the fact that they do not relate strictly to historical or current facts. When used in this Current Report, words such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “strive,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond our control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements. When the Company discusses its strategies or plans, it is making projections, forecasts or forward-looking statements. Such statements are based on the beliefs of, as well as assumptions made by and information currently available to, the Company’s management. Actual results and shareholders’ value will be affected by a variety of risks and factors, including, without limitation, international, national and local economic conditions, merger, acquisition and business combination risks, financing risks, geo-political risks, acts of terror or war, and those risk factors described under the “Risk Factors” section of the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 31, 2026, the Company’s Quarterly Report on Form 10-Q filed with the SEC on May 15, 2026, subsequent Quarterly Reports on Form 10-Q, in the Extension Proxy Statement filed in connection with the Meeting and Amendment on June 16, 2026 (the “Extension Proxy Statement”) and in other reports the Company files with the SEC. Many of the risks and factors that will determine these results and shareholders’ value are beyond the Company’s ability to control or predict.1

1Participants in the Solicitation

~~All~~Plum ~~such~~IV, ~~forward-looking~~the Company ~~statements~~and ~~speak~~their ~~only~~respective asdirectors ofand executive officers may be deemed participants under SEC rules in the ~~date~~solicitation of ~~this~~proxies ~~Current~~from ~~Report~~Plum IV’s shareholders in connection with the Transactions. ~~The~~A ~~Company~~list ~~expressly~~of ~~disclaims~~the ~~any~~names ~~obligation~~of orsuch ~~undertaking~~directors toand ~~release~~executive officers and information ~~publicly~~regarding ~~any~~their ~~updates~~interests orin ~~revisions~~the toTransactions ~~any~~and ~~forward-looking~~their ~~statements~~ownership ~~contained~~of ~~herein~~Plum toIV’s ~~reflect~~securities ~~any~~is, ~~change~~or will be, contained in ~~the~~Plum ~~Company~~IV’s ~~expectations~~ filings with ~~regard~~the ~~thereto~~SEC. orAdditional ~~any~~information ~~change~~regarding inthe ~~events~~interests of the persons who may, ~~conditions~~under orSEC ~~circumstances~~rules, onbe ~~which~~deemed ~~any~~participants ~~such~~in the ~~statement~~solicitation isof ~~based.~~proxies ~~All~~from ~~subsequent~~Plum ~~written or~~IV’s ~~oral~~shareholders ~~forward-looking~~in ~~statements~~connection ~~attributable~~with tothe usTransactions, orincluding ~~persons~~the ~~acting~~names onand interests of the Company’s ~~behalf~~directors ~~are~~and ~~qualified~~executive officers, will be set forth in ~~their~~the ~~entirety~~Proxy Statement/Prospectus, which is expected to be filed by ~~this~~Plum ~~“Cautionary~~IV ~~Note~~and ~~Regarding~~the ~~Forward-Looking~~Company ~~Statements”~~with ~~section~~the SEC. Investors and security holders may obtain free copies of these documents as described above.

~~Participants~~No inOffer ~~the~~ or Solicitation

~~The~~This ~~Company~~Current ~~and~~Report ~~its directors~~is for informational purposes only and ~~executive~~is ~~officers~~not ~~may~~a beproxy ~~deemed~~statement ~~participants~~or ~~under~~solicitation ~~SEC~~of ~~rules~~a proxy, consent or authorization with respect to any securities or in respect of the Transactions and shall not constitute an offer to sell or exchange, or a solicitation of ~~proxies~~an ~~from~~offer to buy or exchange the securities of Plum IV or the Company’s, ~~shareholders~~or any commodity or instrument or related derivative, nor shall there be any sale of any such securities in ~~connection~~any ~~with~~state or jurisdiction in which such offer, solicitation, sale or exchange would be unlawful prior to registration or qualification under the ~~Extension~~securities ~~Amendment~~laws ~~Proposal~~of ~~and~~any ~~related~~such ~~matters~~state or jurisdiction. ~~Information~~This ~~regarding~~Current ~~the~~Report ~~Company’s~~is ~~directors~~not, and ~~executive officers~~under no circumstances is to ~~contained~~be construed as, a prospectus, an advertisement or a public offering of the securities described herein in the ~~Extension~~United ~~Proxy~~States ~~Statement~~or ~~and~~any other jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the ~~Company’s~~requirements ~~filings~~of the Securities Act or an exemption therefrom. Investors should consult with their counsel as to the ~~SEC~~applicable requirements for a purchaser to avail itself of any exemption under the Securities Act.

~~Additional Information~~Forward-Looking ~~and Where to Find It~~Statements

~~The~~This ~~Company~~Current ~~urges~~Report ~~investors,~~and the ~~shareholders~~exhibits ~~and~~attached ~~other interested~~hereto contain ~~persons~~certain toforward-looking ~~read~~statements within the ~~Extension~~meaning ~~Proxy~~of ~~Statement~~the asU.S. ~~well~~federal assecurities ~~other~~laws ~~documents~~with respect ~~filed~~to by the ~~Company~~Transactions ~~with~~and the ~~SEC,~~parties ~~because~~thereto. ~~these~~All ~~documents~~statements contained in this Current Report other than statements of historical ~~will~~fact, ~~contain~~including, ~~important~~without ~~information~~limitation, ~~about~~statements regarding the ~~Company~~Transactions between Plum IV and the ~~Extension~~Company; ~~Amendment~~the ~~Proposal.~~anticipated ~~Shareholders~~benefits ~~may~~and timing ~~obtain~~of ~~copies~~the Transactions; expected trading of the ~~Extension Proxy~~combined ~~Statement,~~company’s ~~without~~securities ~~charge,~~on atthe Nasdaq; the ~~SEC~~building of the Company’s flagship ~~website~~Hell’s atKitchen ~~www.sec.gov~~Project; orthe byanticipated ~~directing~~benefits aand ~~request~~timing toof the Company’s ~~proxy~~flagship ~~solicitor~~Hell’s Kitchen Project, ~~Advantage~~the ~~Proxy,~~combined bycompany’s ~~calling~~future ~~877-870-8565~~financial ~~(toll-free)~~performance; the ability of the combined company to execute its business strategy, orits ~~banks~~market opportunity and ~~brokers~~positioning; ~~can~~and ~~call~~other ~~206-870-8565~~statements regarding management’s intentions, beliefs, or byexpectations ~~emailing~~with ~~[email protected]~~respect to the combined company’s future performance, are forward-looking statements.

NoForward-looking ~~Offer~~statements are oroften ~~Solicitation~~identified by the use of words such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “should,” “will,” “would,” and similar expressions, but the absence of these words does not mean that a statement is not forward-looking.

This Current Report shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended, or an exemption therefrom.2

These forward-looking statements are based on the current expectations and assumptions of Plum IV and the Company and are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such forward-looking statements. Such risks and uncertainties include, but are not limited to: (1) the occurrence of any event, change or other circumstances that could give rise to the termination of the Business Combination Agreement; (2) the outcome of any legal proceedings that may be instituted against the parties following the announcement of the Transactions and any definitive agreements with respect thereto; (3) the inability to complete the Transactions, including due to failure to obtain approval of the shareholders of Plum IV and the Company or other conditions to closing; (4) the risk that the Transactions may not be completed by Plum IV’s business combination deadline and the potential failure to obtain an extension of the business combination deadline if sought by Plum IV; (5) the inability to maintain the listing of Plum IV’s securities or to obtain or maintain the listing of the combined company’s securities on the Nasdaq, the New York Stock Exchange, or another national securities exchange following the Transactions; (6) the risk that the Transactions disrupts the Company’s current plans, business relationships, performance, operations and business generally as a result of the announcement and consummation of the Transactions; (7) the risk that the price of the combined company’s securities may be volatile due to a variety of factors, including changes in laws, regulations, technologies, natural disasters, geopolitical tensions, and macro-economic and social environments affecting its business; (8) the ability to recognize the anticipated benefits of the Transactions, which may be affected by, among other things, competition, the ability of the combined company to grow and manage growth profitably and retain its key employees; (9) costs related to the Transactions; (10) changes in applicable laws or regulations; (11) risks related to the Company’s business, including fluctuations in demand and prices for lithium and other critical minerals, competition within the industry, the risks inherent in development projects and exploration activities, potential delays or cost overruns in capital expenditures, the ability to secure necessary raw materials, compliance with regulatory requirements, environmental and safety obligations, economic and market conditions, and political or geopolitical developments; and (12) other risks detailed from time to time in Plum IV’s filings with the SEC, including the Registration Statement and related documents filed or to be filed in connection with the Transactions.

~~SIGNATURE~~The foregoing list of risk factors is not exhaustive. You should carefully consider the foregoing factors and the other risks and uncertainties described in the “Risk Factors” section of Plum IV’s Annual Report on Form 10-K filed with the SEC on March 31, 2026, Plum IV’s Quarterly Report on Form 10-Q filed with the SEC on May 15, 2026, subsequent Quarterly Reports on Form 10-Q and the Registration Statement and Proxy Statement/Prospectus that will be filed by Plum IV and the Company, and other documents filed by Plum IV from time to time with the SEC, as well as the list of risk factors included herein. These filings identify and address other important risks and uncertainties that could cause actual results to differ materially from those contained in the forward-looking statements. Additional risks and uncertainties not currently known or that are currently deemed immaterial may also cause actual results to differ materially from those expressed or implied by such forward-looking statements. Readers are cautioned not to put undue reliance on forward-looking statements, and none of the parties or any of their representatives assumes any obligation and do not intend to update or revise these forward-looking statements, each of which is made only as of the date of this Current Report.

~~Pursuant~~Item to9.01. ~~the~~Financial ~~requirements of~~Statements ~~the~~and ~~Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized~~Exhibits.

Date: July 9, 2026	PLUM ACQUISITION CORP. IV
	By:	/s/ Kanishka Roy
	Name:	Kanishka Roy
	Title:	Chief Executive Officer

(d) Exhibits.

Exhibit No.		Description
10.1†		Amendment No. 2 to the Business Combination Agreement, dated July 6, 2026, by and among Plum Acquisition Corp. IV, Plum IV Merger Sub Inc. and Controlled Thermal Resources Holdings Inc.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

†	Certain of the exhibits and schedules to this exhibit have been omitted in accordance with Regulation S-K Item 601(b)(2). The Registrant agrees to furnish supplementally a copy of all omitted exhibits and schedules to the SEC upon its request.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: July 10, 2026	PLUM ACQUISITION CORP. IV

	By:	/s/ Kanishka Roy
	Name:	Kanishka Roy
	Title:	Chief Executive Officer

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