Germany’s uneasy energy truce with Washington is starting to fray, and the pressure point is a single refinery that keeps Berlin moving. Managers at the PCK Schwedt refinery, majority-owned by Russia’s Rosneft (54.17%), have privately warned the German government that U.S. sanctions are already choking day-to-day operations and could threaten fuel supplies for Berlin and eastern Germany. In a January letter to economy and energy minister Katherina Reiche, refinery management made what they described as an urgent appeal to resolve the…