Superconductivity at 20Â K in yttrium metal at pressures exceeding 1Â Mbar

In experiments in a diamond anvil cell, yttrium metal is found to display a superconducting transition temperature in the ac susceptibility which increases monotonically from 3.5 K at 30 GPa to 19.5 K at 115 GPa, where the transition onset lies at 20 K. This is the second highest value of Tc ever observed for an elemental superconductor. A fit to the Y data using the McMillan equation is consistent with electron-phonon superconductivity with moderately strong coupling.