Ex-Brevan Howard Trader Sued by Quant Who Joined His New Fund

(Bloomberg) -- Ex-Brevan Howard Asset Management portfolio manager Robert Sicari was accused of withholding millions of dollars in promised trading profits from a former colleague who joined his new fund.

Wooyoung Hong, who worked under Sicari at Brevan Howard as a quantitative researcher, said in a complaint filed Tuesday in New York that they were both fired from that firm in 2024. Sicari subsequently approached Hong about joining ThirtyPark Capital, the fund he was starting to invest his own money, according to the suit.

Hong claims Sicari promised to pay him 50% of the gains from certain trades and give him a 30% stake in ThirtyPark. In his suit, Hong estimates that he’s entitled to as much as $3.5 million for trades he handled from November 2024 to December 2025 but says Sicari kept the money to try to force him to renegotiate the equity portion of their deal.

Reached Tuesday, Sicari had no immediate comment beyond saying that ThirtyPark is no longer operating. He didn’t reply to follow-up messages on Wednesday. A lawyer for Sicari declined to comment.

The complaint paints a portrait of traders adjusting after their exit from a major hedge fund. According to the suit, Hong was dismissed from Brevan Howard as the only direct report to Sicari, whom he called his mentor. Hong says Sicari managed a portfolio of hundreds of millions of dollars at Brevan Howard, while ThirtyPark was “substantially smaller.”

Brevan Howard declined to comment on Wednesday.

Hong, who received a doctorate in physics from Harvard and previously worked at Alphabet Inc.’s Google, joined Brevan Howard in 2023, earning a $400,000 base salary, according to the suit. He says that he and Sicari became close, including spending weekends together, and discussed other opportunities to collaborate, either at another firm or by launching one of their own.

“Whatever we do, we’ll do it together,” Sicari repeatedly told Hong, according to the suit.

Hong claims that became the plan once they were both fired from Brevan Howard. At ThirtyPark, Sicari allegedly promised to cover losses, margin interest, commissions and operational costs while Hong developed trading infrastructure and technical support. Hong says they came up with the 50% profit-sharing and 30% stake to provide him with “compensation commensurate with the value and opportunity cost of his services while limiting Mr. Sicari’s fixed cash expenditures.”

Among the successful trades to which Hong claims he’s entitled to profits are some tied to Coreweave Inc.’s failed $9 billion takeover of Core Scientific Inc., Chevron Corp.’s acquisition of Hess Corp., and the Paramount Global-Skydance Media merger. The largest claim stems from a bet on US Steel Corp., which was then being acquired by Nippon Steel Corp. Hong says those trades returned about 80%, entitling him to $1.2 million to $2 million.

But Sicari allegedly tried to alter the terms of their deal in January, citing the need to conserve early-stage capital. According to the suit, he proposed that Hong instead accept a $400,000 cash payment and a 30% profit share that would vest over time. Hong says he objected to the new offer.

Hong says he recorded conversations in which Sicari argued for the new deal.

“Who’s eating all the commission?” Sicari allegedly asked in a Jan. 6 call. “And also, like, margin. It’s like I’m being super generous.”

In another conversation a week later, Hong claims Sicari acknowledged the quant had earned his compensation but asked him “to work with me on this percentage thing.”

Hong says the two men agreed to take a few days to calm down and see if they could reach an agreement. Later that month, however, Sicari suddenly cut off Hong’s access to the firm’s systems, according to the suit. Hong says he was only paid $20,000 for his year of work at ThirtyPark.

“In America, when you work, you should be paid,” Juannell Riley, a lawyer for Hong, said in an interview.

The case is Hong v Sicari, New York State Supreme Court, New York County.

More stories like this are available on bloomberg.com

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