Plot line in Eifelheim was that the aliens needed finely drawn copper wire to fix their ship. Won't spoil it, but aliens crash land in the Black Forest, 1349. (Don't read the Wiki, jump in, trust me.)

There's a smaller plot of a modern couple, a scholar and a physicist, trying to figure out why that piece of land was never resettled.

Amazing book, stumbled on it by dumb luck. The author shows off his medieval knowledge a great deal, little heavy handed, but that's part of the fun. "See! That's where that word/practice/belief comes from!"

The protagonist is a Jesuit priest who serves the tiny village. Weird to have one so educated in such a place, but that's part of the plot. Amazing to read what they knew then, what they didn't, but almost nothing is left to blind superstition.