Co3Ga2Ge5: Probing site mixing of the Ru3Sn7 structure type with elements difficult to distinguish by diffraction

Co3Ga2Ge5 was synthesized through arc-melting stoichiometric ratios of the elements, and a Ru3Sn7-type structure was confirmed by X-ray diffraction. Because Co3Ga2Ge5 contains Ga and Ge, which have very similar X-ray and neutron scattering factors, any Ga/Ge crystallographic site preference cannot be determined with diffraction alone. The purpose of this study is to highlight the importance of using multiple techniques to characterize otherwise structurally ambiguous intermetallic compounds. We utilize 71Ga nuclear magnetic resonance spectroscopy and an analysis of the X-ray absorption fine structure to clarify the amount of Ga/Ge site mixing. Our combined use of X-ray diffraction and spectroscopy provides a comprehensive structural analysis of Ga site mixing across the Ge crystallographic sites, enhancing the understanding of the structure and properties of Co3Ga2Ge5. [Display omitted] •A ternary analogue of the Ru3Sn7 structure type was synthesized with elements that have very similar scattering factors.•A combination of XRD, 71Ga NMR, and Ga/Ge EXAFS were used to probe the Ga substitution.•Our method using diffraction and spectroscopy effectively characterized an ambiguous compound.•Co3Ga2Ge5 is a temperature-independent paramagnet, with a metallic resistivity.