The critical temperature of superconductor and its electronic specific heat

It is shown that the critical temperature of the superconductor is related to the Sommerfeld constant, i.e. it is determined by the Fermi energy for I-type superconductors. The estimation of properties of II-type superconductors reveals a somewhat different relation of critical temperature and Fermi energy. Among the high-temperature superconducting ceramics there are the both - I and II - types superconductors.