BERLIN, Jan 13 (Reuters) - The German government last year posted its biggest surplus since reunification in 1990, the Finance Ministry said on Monday, adding that this was partly due to interest payments being lower.

A fund set aside for helping to integrate migrants now contains 48.2 billion euros ($53.61 billion), of which around two-thirds have already been earmarked for use, the ministry said. It said there were around 17.1 billion euros in that fund still available for use.