Novel derivatives of the CaIn2 type of structure:: Yb1+xMg1-xGa4 (0≤x≤0.058) and YLiGa4

The compounds Yb1+xMg1-xGa4 (0 less than or equal to x less than or equal to 0.058) and YLiGa4 were synthesized by direct reaction of the elements in sealed niobium crucibles. The atomic arrangement of Yb1+xMg1-xGa4 (x = 0.058) represents a new structure type (space group P6m2, a = 4.3979(3) Angstrom and c = 6.9671(7) Angstrom) as evidenced by single crystal structure analysis and can be described as an ordered variant of CaIn2. YLiGa4 is isotypic to the ytterbium compound according to X-ray Guinier powder data (a = 4.3168(1) Angstrom and c = 6.8716(2) Angstrom). Measurements of the magnetic susceptibility of both compounds reveal intrinsic diamagnetic behaviour, i.e., ytterbium in the 4f(14) configuration for Yb1+xMg1-xGa4 (x = 0). From electrical resistivity data both compounds can be classified as metals. The compressibility of Yb1+xMg1-xGa4 (x = 0.058) as measured in diamond anvil cells by angle-dispersive X-ray diffraction is compatible with a valence change of the ytterbium atoms at high-pressures and indicates a slight anisotropy which is in accordance with the structural organisation of the gallium network. X-ray absorption spectra of the Yb L-III edge of Yb1+xMg1-xGa4 (x = 0.058) at pressures up to 25.0 GPa show a two-peak structure which reveals the presence of Yb in the 4f(14) and 4f(13) states. The amount of ytterbium in the 4f(13) state increases in two steps with progressing compression. The bonding analysis by means of the electron localization function reveals the Zintl-like character of both compounds and confirms the 4f(14) state for the majority of ytterbium atoms.