I remember reading the book 15-20 years ago although I believe the book was much older than that. It is about a German tank from WWII which was made from some special (magical?) metal from some mountain in Germany. The tank appeared to be sentient in some way and had an amazing kill ratio in the war. The book is set in occupied Germany, probably the 1950s and the tank leaves some museum or something of the sort heading to the mountains. An American tracks the tank and eventually destroys it in the mountains where the special metal was originally mined/forged. I seem to remember there being a love interest of the American involved in some way although that recollection is rather fuzzy.
I believe the tank may have been a Jagdpanzer. Anyone recalls the name of the book?