Superconductivity was discovered by Kamerlingh Onnes in 1911, in a metal solid. Ever since, researchers have attempted to observe superconductivity at increasing temperatures with the goal of finding a room-temperature superconductor. By the late 1970s, superconductivity was observed in several metallic compounds (in particular Nb -based, such as NbTi, Nb 3 Sn, and Nb 3 Ge) at temperatures that were much higher than those for elemental metals and which could even exceed 20 K (−253.2 °C).