'Pd₂₀Sn₁₃' revisited: Crystal structure of Pd_6.69Sn_4.31

The crystal structure of the title compound was previously reported with composition 'Pd₂₀Sn₁₃' [Sarah et al. (1981). Z. Metallkd, 72, 517-520]. For the original structure model, as determined from powder X-ray data, atomic coordinates from the isostructural compound Ni₁₃Ga₃Ge₆ were transferred. The present structure determination, resulting in a composition Pd_6.69Sn_4.31, is based on single crystal X-ray data and includes anisotropic displacement parameters for all atoms as well as standard uncertainties for the atomic coordinates, leading to higher precision and accuracy for the structure model. Single crystals of the title compound were obtained via a solid-state reaction route, starting from the elements. The crystal structure can be derived from the AlB₂ type of structure after removing one eighth of the atoms at the boron positions and shifting adjacent atoms in the same layer in the direction of the voids. One atomic site is partially occupied by both elements with a Pd:Sn ratio of 0.38 (3):0.62 (3). One Sn and three Pd atoms are located on special positions with site symmetry 2. (Wyckoff letter 3a and 3b).