Ru3Sn7 with the Ir3Ge7 structure-type

Millimeter-sized single crystals of the title compound have been grown from a Sn-rich melt and neutron diffraction data recorded at room temperature and 20 K have been used to confirm and refine the crystal structure. The Ir3Ge7 structure-type, cubic Im (3) over bar m can be viewed as a framework of alternating corner linked Ru6Sn8 capped-octahedral clusters and Ru3Sn4 flattened-octahedral clusters, such that the latter form their own three-dimensional sublattice. The Ru-Sn distances determined for Ru3Sn7 fall in the middle of the observed range tabulated from the handful of known Ru-Sn distances in intermetallics. The resistivity of Ru3Sn7 is metallic, with a value of 72 mu Omega cm at 300 K and 0.5 mu Omega cm at 5 K. The magnetic susceptibility is diamagnetic at room temperature, but becomes paramagnetic as the temperature is lowered. We interpret the susceptibility as being due to a diamagnetic 'core' contribution and a paramagnetic contribution arising from the Ru d orbitals. (C) 1998 Elsevier Science S.A. All rights reserved.