By David Lawder BONN, Germany (Reuters) -The United States does not have legal authority to seize Russian central bank assets frozen due to its invasion of Ukraine, Treasury Secretary Janet Yellen said on Wednesday, but talks with U.S. partners over ways to make Russia foot the bill for Ukraine’s post-war reconstruction are starting. Yellen also said it is likely that the special license granted to allow Russia to make payments to its U.S. bondholders would not be extended when it expires next week, leaving Russian officials a fast-narrowing window to avoid its first external debt default sinc…