By Jonathan Stempel

NEW YORK, March 28 (Reuters) - A U.S. judge on Tuesday significantly narrowed private litigation accusing several big banks and German chemical giant BASF SE (BASFn.DE) of conspiring to suppress platinum and palladium prices.

U.S. District Judge Gregory Woods in Manhattan dismissed claims against BASF, Switzerland's UBS Group AG (UBSG.S) , South Africa's Standard Bank Group Ltd (SBKJ.J) and the London Platinum and Palladium Fixing Co.

In a 104-page decision in the proposed class-action case, Woods said dismissal was appropriate because of a lack of proof these defendants conspired to fix prices, had sufficient ties to the United States, or both.

The judge also dismissed claims that Goldman Sachs Group Inc (GS.N) and HSBC Holdings Plc (HSBA.L) violated the U.S. antitrust law known as the Sherman Act, saying the plaintiffs were not "efficient enforcers" of that law.

Woods said the plaintiffs may pursue some price manipulation claims against Goldman and HSBC under the Commodities Exchange Act, citing their allegations that the defendants "engaged in conscious misbehavior or, at least, acted with recklessness."

Merrill Davidoff, a lawyer for the plaintiffs, in an email declined immediate comment, citing a need to review the decision.

Platinum and palladium are used in catalytic converters to curb vehicle emissions, and are also used in dentistry and jewelry.

The U.S. lawsuit is one of many where private plaintiffs have sought to hold banks and other defendants liable for rigging interest rates, commodities and currencies, separate from any punishments that regulators might seek to impose.

Purchasers of platinum, palladium and futures contracts for the metals accused the defendants of having from Jan. 1, 2008 to Nov. 30, 2014 conspired to rig the twice-daily platinum and palladium "fixings" and the prices of futures and options based on those fixings.

According to the complaint, the alleged misconduct included illegal sharing of customer data, using that data to engage in "front-running" of expected price moves, and manufacturing phantom "spoof" orders.

While the London Metal Exchange launched a new electronic fixing process on Dec. 1, 2014, the plaintiffs said this did not excuse the defendants from owing unspecified millions of dollars for their earlier losses.

The case is In re: Platinum and Palladium Antitrust Litigation, U.S. District Court, Southern District of New York, No. 14-09391.

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