Possible type of heavy-electron superconductivity in PrOS4Sb12

Unconventional nature of superconducting state of PrOs4Sb12, Pr-based heavy-electron compound with the filled Skutterudite structure, is shown to be explained by taking into account a structure of the crystalline-electric-field level and of the Fermi surface determined by the band structure calculation. In particular, the anisotropic pairing with a full gap on the Fermi surface, suggested by the measurement of the NQR relaxation rates 1/T-1, is shown to be possible in the manifold of chiral "p"- or "d"-wave pairing, and to be compatible with the absence of the coherence peak and the pseudo-gap behavior of I/T1T far above the superconducting transition temperature. (C) 2003 Elsevier Science B.V. All rights reserved.