Superconductivity of Uranium

A ballistic mutual-inductance technique has been employed to investigate the magnetic susceptibility of two uranium samples down to a temperature of 0.1°K. Both samples exhibited a superconducting transition in zero magnetic field at a temperature ($T_c$) of 0.68±0.02°K. The transitions were not sharp, being spread over a temperature interval of 0.45°K. The critical magnetic field of one of the samples was measured down to 0.37°K and a value of 720 gauss/deg was obtained for ${\left(\frac{\mathrm{dH}}{\mathrm{dT}}\right)}_{T=T_c}$. Consideration is given to the values of the electronic specific heat coefficients derived from the critical magnetic field data for uranium and titanium.