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 Im3m can be viewed as a framework of alternating corner linked Ru₆Sn₈ capped-octahedral clusters and Ru₂Sn₄ 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 μΩ cm at 300 K and 0.5 μΩ 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.