Superconductivity ofα-Uranium and Uranium Compounds at High Pressure

The pressure dependence of the superconducting transition temperature $T_c$ of $\alpha$-uranium has been measured to a maximum pressure of 22 kbar and constitutes an important extension of the pressure range of previous measurements. It has been observed that $T_c$ increases rapidly as a function of pressure up to ∼9 k bar, passes through a broad maximum, and then decreases. A possible explanation of this behavior is offered on the basis of a pressure-induced transformation in the electronic properties of uranium. Data are also reported for observations of the $T_c$ under pressure of the compounds ${\mathrm{U}}_6$Fe and ${\mathrm{U}}_6$Mn and the solid solution alloy ${\mathrm{U}}_{0.85}$ ${\mathrm{Mo}}_{0.15}$.