Pressure Effect and Thermal Expansion for Superconducting Tin

The superconducting critical field curve of white tin has been measured between 1.15° and 3.7°K at pressures up to 2800 bars using solid helium as the pressure transmitter. The results at $T_c$ agree with previous work at this Laboratory. An analysis of the data indicates a relatively small pressure dependence of the electronic specific heat coefficient $\gamma$, and, consequently, a small electronic contribution to the thermal expansion in the normal state. The thermal expansion in the superconducting state is predicted to be large and negative, and extremely anisotropic. The deviation of the superconducting properties of tin from "simple similarity" is discussed.