BERLIN (Reuters) - Leaders of Germany s Social Democrats have voted unanimously to begin exploratory talks with Chancellor Angela Merkel s conservatives about forming a coalition government, Andreas Nahles, head of the SPD s parliamentary group, said on Friday. Nahles said party leaders would work on substantive issues in the talks, with a party conference in January to determine the way forward. She said the SPD, which suffered its worst post-war election losses in September, planned to enter the talks with an open and constructive attitude with an eye to improving the lives of ordinary Germans.  