Lehman Brothers Holdings is claiming $500m from Barclays for allegedly failing to pay all of the bonuses agreed to when it bought the defunct investment firm's North American business.
Lehman wrote a letter to US bankruptcy Judge James Peck saying an opinion he wrote in February showed Barclays "breached its bonus payment obligations."
The letter was filed in U.S. Bankruptcy Court in Manhattan on 29 April, according to Bloomberg.
Barclays has said it paid the full $2bn it promised, including non-bonus compensation.
Peck issued the February opinion in a lawsuit that Lehman lost seeking $11bn from Barclays over the deal.
Peck's ruling, which followed a trial with more than 30 days of testimony, exonerated Barclays from having contrived to make a "windfall" on the purchase as Lehman alleged.
The ruling left the two sides still fighting over what is owed to whom.
Separately, the trustee for Lehman's brokerage is in a dispute with Barclays over $3.5bn in assets after Peck failed to specify how much Barclays was entitled to when it bought the North American business in September 2008.
Barclays declined to comment.
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