Barclays, Deutsche Bank and three other banks have been accused of manipulating the London gold fix, a benchmark used throughout the $20 trillion market for the metal. Kevin Maher, a New York resident who says he bought and sold gold and gold futures and options, filed a suit in Manhattan federal court claiming the five banks overseeing the century-old benchmark colluded to manipulate it. Maher’s complaint cites press reports, including a Bloomberg News story on a draft paper by two researchers showing unusual pricing patterns connected to the gold fix. The paper is the first study to raise the possibility that the banks, which also include Bank of Nova Scotia, HSBC Holdings and Societe Generale, may have been actively working together to manipulate the benchmark. Maher is seeking to represent a class of all investors who, from 2004 to now, held or traded gold and gold derivatives that were priced based on the gold fix or who held or traded COMEX gold futures or options. He’s seeking unspecified damages on behalf of the class. Damages may be tripled under U.S. antitrust law.