The CEO of Arconic has stepped down after an ugly battle with hedge fund titan Paul Singer

U.S. specialty metals maker Arconic Inc's chief executive, Klaus Kleinfeld, has resigned, following attempts by activist hedge fund Elliott Management to overthrow the company's directors and top executives.

Arconic said Kleinfeld stepped down after the board learned he had sent a letter to a senior officer of Elliott Management without consulting the board.

The company also said in a statement that it had not made the decision in reponse to Eliott's criticisms. Elliott, a New York activist hedge fund led by Paul Singer, has been waging an activist campaign against the company for months. A spokesman for Elliott didn't immediately comment.

Board member David Hess has been appointed as interim CEO, Arconic said.

Arconic's stock price has jumped on the news, rising about $1 in value from $26 per share at the start of Monday morning, according to Markets Insider data.