Ian Tregillis entitled "Bitter Seeds". The minute I heard the premise, I was hooked.
It's an alternate WWII history where a Nazi scientist has managed to imbue some German psycopaths with x-men-like powers and the Wermacht is unstoppable! (Even more so than in real history).
To counter this, the British government drafts an elite unit of Warlocks to fight the Nazi supermen.
Warlocks versus metahumans? Nazi metahuman! How awesome is that?!?