ELECTRONIC BAND-STRUCTURE STUDY OF THE TRANSPORT-PROPERTIES OF THE INTERMETALLIC COMPOUNDS ZRRUP AND ZRRUSI

Electrical properties of the intermetallic superconductors h-ZrRuP, o- ZrRuP, and h-ZrRuSi were examined by calculating their electronic stru ctures on the basis of the extended Huckel tight-binding method. To a first approximation, the electronic structure of ZrRuP is well describ ed in terms of the oxidation state Zr4+(RuP)(4-). This picture provide s simple explanations for why both h-ZrRuP and o-ZrRuP have low N(E-f) values and why h-ZrRuP has a nearly half-filled one-dimensional (1D) band dispersive along the c direction. A charge density wave instabili ty associated with such a 1D band probably causes a c-axis doubling st ructural distortion in h-HfRuAs and h-TiRuAs. We discussed probable re asons for why the intermetallic phases with the c-axis doubling distor tion are not superconductors and why h-ZrRuP has a higher T-c than doe s o-ZrRuP.