Philip Falcone is stepping down as chairman and chief executive officer of Harbinger Group Inc., the public holding company in which his hedge fund owns a stake, as Harbinger’s biggest shareholder exerts more control, Bloomberg News reported yesterday. Leucadia National Corp., already the biggest single owner of Harbinger Group, bought an additional 5 million shares, bringing Leucadia’s stake to about 22 percent. Falcone said he plans to focus on his role as chairman of HC2 Holdings Inc., which owns stakes in a range of companies, much like Harbinger Group.