PHASES AROUND THE 1 1/1-COMPOSITION IN THE YB-AU-GE AND CA-AU-GE SYSTEMS/

The systems YbAu2-xGex and CaAu2-xGex with 0.7<x<1.3 were structurally examined by X-rays on powders and single crystals. In this range of c omposition nine phases occur, belonging to six closely related structu re types: CeCu2, AlB2, EuAuGe (occupation derivative), SrAgGe alpha-Yb AuGe and beta-YbAuGe (the last two being centrosymmetric variants of t he CaCuGe type). The equiatomic compound CaAuGe shows a phase transiti on at 1238 K. YbAuGe crystallizes in three different structural modifi cations as a function of. temperature: alpha-YbAuGe up to 1003 K, beta -YbAuGe in the range 1003 to 1308 K and gamma-YbAuGe at T>1308 K. Resi stance measurements carried out in the range 14-400 K for the high-tem perature forms of YbAuGe and CaAuGe show normal metallic behaviour. Ma gnetic susceptibility data of YbAuGe are in agreement with the occurre nce of divalent ytterbium. (C) 1998 Elsevier Science S.A.