Ternary Rare Earth Metal Gold Stannides and Indides with Ordered U 3Si2 and Zr3Al2-Type Structure

The new ternary stannides RE2Au2Sn (RE = Gd, Tb) and indides R E2Au2In (RE = Y, G d-T m , Lu) were synthesized by arc-melting of the elemental components and subsequent annealing at 800 °C. While Gd2Au2Sn, Tb2Au2Sn and the indides with RE = Y, G d -E r crystallize in the ordered U3Si2 structure, Tm2Au2In and Lu2Au2In adopt the ordered Zr3Al2 structure, respectively. The crystal structure of Dy2Au2In was refined from single-crystal Xray data: P4/mbm. Z = 2, a = 784.1(1) pm, c = 373.9(1) pm, V = 0.2299 nm3 and R = 0.028 for 342 F2 values and 12 variables. The tin (indium) atoms in these compounds occupy [RE8] square prisms and the gold atoms are surrounded by [RE6] trigonal prisms. These fragments are derived from the A1B2 and CsCl-type structures. The crystal chemistry of these com­ pounds is briefly discussed.