If you want some double-dealing,
Walter Schellenberg is the German you need. He was authorised to act on behalf of Himler in all matters, and was the man who arranged prisoner releases through the Swedish Red Cross. He seems to have believed that such small-scale gestures would allow Himler to negotiate with the Allies and become leader of a conquered Germany.
As he doesn't seem to have subscribed to Himler's mystical ideas, he might very well do a deal to allow the Allies to steal magical artifacts, but get caught out by someone lower in the hierarchy who wasn't prepared to co-operate.