Aluminum

Aluminum (also spelled aluminium) is a chemical element, number 13 on the periodic table.

One of the primary metals used in the construction of Amelia Earhart's Lockheed L-10 Electra was, among other things, an aluminum alloy. 

For Vosk to implement the construction of his Na'kuhl plasma pulse weapons, in an alternate timeline, he required the Germans to divert 86 metric tons of aluminum plating and 170 tons of carbon steel.