New TiNiSi-type RMgAg and RMgPd with R=Ca, Yb, and MgZn2-type Ca(Mg,Ag)2 compounds

The phases CaMgAg, YbMgAg, CaMgPd, and YbMgPd were synthesized by melting the constituent metals in sealed tantalum crucibles and by annealing at 1023 K. All the samples were homogeneous, and the crystallographic analysis, which was performed by powder and singlecrystal techniques, shows that the four compounds are isotypic and belong to the orthorhombic TiNiSi type. Magnetic measurements showed that YbMgAg and YbMgPd behave like Pauli paramagnets, according to the divalency of Yb in both phases. Within the Ca-Mg-Ag system, the existence range of the MgZn₂-type phases in the Mg-rich CaMg_2−x Ag _x pseudobinary system goes from CaMg₂ to CaMg_1.6Ag_0.4. Another stability region of the MgZn₂ structure occurs around the Ag-rich composition (Ca_0.94Mg_0.06)(Ag_1.60Mg_0.40), where magnesium replaces both the Ca and Ag atoms.