High-Temperature Superconducting Phase in Clathrate Calcium Hydride CaH 6 up to 215 K at a Pressure of 172 GPa The recent discovery of superconductive rare earth and actinide superhydrides has ushered in a new era of superconductivity research at high pressures. This distinct type of clathrate metal hydrides was first proposed for alkaline-earth-metal hydride CaH_{6} that, however, has long eluded experimental synthesis, impeding an understanding of pertinent physics. Here, we report successful...