COLUMBIA, S.C. — Century Aluminum is appealing a judge’s dismissal of its federal lawsuit accusing South Carolina’s state-owned utility of unfair trade practices related to the company’s smelter.

Court documents show the company filed an appeal Tuesday in their case against Santee Cooper.

Century said in 2015 it would have to close the plant unless it reached a new contract with the utility. Over the next year, Century says Santee Cooper unlawfully forced the Mount Holly plant to buy 25 percent of its power at rates well above market prices.

The company says that move ultimately forced Mount Holly to lay off half of its 600 employees to stay afloat.

The lawsuit sought unspecified monetary damages, as well as an injunction against Santee Cooper’s behavior.

A judge dismissed the case last week.