  We report the observation of conventional superconductivity at the highest
temperature yet attained without mechanical compression, around 54 kelvin in
palladium-hydride and 60 kelvin in palladium-deuteride. The remarkable increase
in Tc compared to the previously known value was achieved by rapidly cooling
the hydride and deuteride after loading with hydrogen or deuterium at elevated
temperature. Our results encourage hope that conventional superconductivity
under ambient conditions will be discovered in materials with very high
hydrogen density, as predicted more than a decade ago.
