RMX COMPOUNDS FORMED BY ALKALINE-EARTHS, EUROPIUM AND YTTERBIUM .4. TERNARY PHASES WITH M=AG AND X=SI, GE, SN, PB

The ternary RAgX phases, with R = Ca, Sr, Ba, Eu, Yb and X = Si, Ge, S n, Pb, were structurally studied by means of X-ray diffraction on powd ers and single crystals. The tin and lead compounds exist on the equia tomic composition and crystallize in the CeCu2, CaLiSn and YbAgPb type s. The silicon and germanium compounds are in most cases nonstoichiome tric and belong to the CeCu2 and AlB2 types, and to three new variants of the AlB2 structure: SrAgGe, Ba3Ag2Si3, Ca5Ag2Si7. The influence of the electron concentration factor on the stability of the different a tomic arrangements is pointed out.