The superconductive transition temperature of binary and ternary solid solutions in thallium

The transition temperatures of various binary alloys and of ternary alloys in the system Tl Hg _x Sn _y were investigated. By analysing the results different anisotropy parameters were obtained. This was explained by a nonlinear valence dependence of the transition temperature, which can be caused by changes in the topology of the Fermi surface.