A brief comparison of superconductivity in borocarbides and cuprates

The challenge of the present knowledge of the electronic structure and sele cted thermodynamic properties on the mechanism of superconductivity in rare -earth transition metal borocarbides (nitrides) is discussed with respect t o somewhat unexpected similarities with as well as to clear differences fro m the cuprate superconductors. The effect of substitutional nonmagnetic and magnetic disorder in the rare-earth intermediate layer in between the tran sition metal boron networks as well as in the network itself upon various t hermodynamic properties in the superconducting state of YxR1-xC(Ni1-yPtyB)( 2) R = Lu or Tb is studied theoretically as well as experimentally. The sup pression of the upper critical field and its positive curvature near T-c ca n be used as highly sensitive measures of the degree of disorder. (C) 2001 Elsevier Science B.V. All rights reserved.