Widely Spaced Planes of Magnetic Dimers in the Ba6Y2Rh2Ti2O17-{δ} Hexagonal Perovskite

We report the synthesis and initial characterization of Ba6Y2Rh2Ti2O17-{\delta}, a previously unreported material with a hexagonal symmetry structure. Face-sharing RhO6 octahedra form triangular planes of Rh2O9 dimers that are widely separated in the perpendicular direction. The material displays a small effective magnetic moment, due to the Rh ions present, and a negative Curie-Weiss temperature. The charge transport and optical band gaps are very similar, near 0.16 eV. A large upturn in the heat capacity at temperatures below 1 K, suppressed by applied magnetic fields larger than {{\mu}0H = 2 Tesla, is observed. A large T-linear term in the specific heat ({\gamma}=166 mJ/mol f.u-K2) is seen, although the material is insulating at low temperatures. These results suggest the possibility of a spin liquid ground state in this material.