Minority investors in West Palm Beach-based Oxbow Carbon, fresh off a major Delaware Court of Chancery victory, are investigating up to $50 million in payments made by the company to attorneys for founder and CEO William Koch at Mintz, Levin, Cohn, Ferris, Glovsky and Popeo.

Robert J. Hurst and Barry Volpert, principals in Crestview-Oxbow Acquisition LLC, said in a books-and-records complaint Wednesday that they were targeting ”corporate waste and inappropriate spending” on Mintz Levin, claiming the law firm served Koch’s interests despite agreeing to represent Oxbow in a two-year suit over Crestview’s right to force Oxbow’s sale.