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Abstract:
The three intermetallic compounds SrAuGa, BaAuAl and BaAuGa were synthesised from the elements in niobium ampoules. The Sr compound crystallises in the orthorhombic KHg2-type structure (Imma, a=465.6(1), b=771.8(2), c=792.6(2) pm, wR(2)=0.0740, 324 F-2 values, 13 variables), whereas the Ba compounds were both found to crystallise in the cubic non-centrosymmetric LaIrSi-type structure (P2(1)3, BaAuAl: a=696.5(1) pm; wR(2)=0.0427, 446 F-2 values, 12 variables; BaAuGa: a=693.49(4) pm, wR(2)=0.0717, 447 F-2 values, 12 variables). The samples were investigated by powder X-ray diffraction and their structures refined on the basis of single-crystal X-ray diffraction data. The title compounds, along with references from the literature (CaAuAl, CaAuGa, CaAuIn, and SrAuIn), were characterised further by susceptibility measurements and Al-27 and Ga-71 solid-state NMR spectroscopy. Theoretical calculations of the density of states (DOS) and the NMR parameters were used for the interpretation of the spectroscopic data. The electron transfer from the alkaline-earth metals and the group 13 elements onto the gold atoms was investigated through X-ray photoelectron spectroscopy (XPS), classifying these intermetallics as aurides.
