Synthesis and structure of YbCuGe and YbIrGe

The equiatomic ytterbium-transition metal-germanides YbCuGe and YbIrGe were synthesized in single crystalline form from CuGe and IrGe master alloys and ytterbium via the Bridgman technique and they were characterized through their X-ray powder patterns. The structures were refined from X-ray single crystal diffractometer data: NdPtSb type, P6₃mc, a = 421.36(8), c = 703.9(1) pm, wR2 = 0.0234, 210 F² values, 11 variable parameters, BASF = 0.35(9) for YbCuGe and TiNiSi type, Pnma, a = 671.09(6), b = 421.55(5), c = 757.16(7) pm, wR2 = 0.0782, 519 F² values, 20 variable parameters for YbIrGe. The copper (indium) and germanium atoms build up [CuGe] and [IrGe] networks. In YbCuGe the two-dimensional [CuGe] network consists of puckered layers of Cu₃Ge₃ hexagons (247 pm Cu-Ge) that are charge balanced and separated by the ytterbium atoms. In contrast, the ordered Ir ₃Ge₃ hexagons show a strong orthorhombic distortion and the [IrGe] network is three-dimensional with a distorted tetrahedral germanium coordination around iridium with almost equal Ir-Ge distances (252-259 pm). The ytterbium atoms fill cages within this network. The cell volumes of YbCuGe and YbIrGe are indicative for purely trivalent ytterbium.