UNUSUAL ANISOTROPY MECHANISM IN CE-PNICTIDES DUE TO VIRTUAL VALENCE FLUCTUATION

est expliquee par un melange anisotrope des etats 4f et des electrons de valence. Ceci est compatible avec le fait qu'une telle anisotropie n'a pas 6t6 mise en evidence dans d'autres pnictures de cerium. Abstract.--- Unusual strong magnetic anisotropies in CeBi and CeSb are explained based on the anisotropic mixing mechanism between the 4f states and the valence electrons, This is consistent with the fact that no such strong anisotropy isfbund in other Ce-pnictides. Ce-pnictides are interesting materials showing various unusual anomalous properties. In CeN, Ce is believed to be tetravalency and thus non-magnetic /l/, while in CeP, Ce Cs trivalency and thus the real valence fluctuation is expected to occur in their alloys /2/. They are also interesting in the sense of narrow gap semiconductor. The ga