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A new S = 1 kagom e compound based on vanadium(III) is reported. The structure was refined simultaneously against single-crystal neutron and X-ray diffraction data, as a gaudefroyite-type with a new supercell (a 0 = 2a þ b, b 0 = -a -2b, c 0 = c) driven by the ordering of columns of isolated triangular BO 3 3ions. Low-temperature neutron powder diffraction and magnetic (dc and ac susceptibility) data rule out the presence of long-range magnetic order above at least 1.5 K, but specific heat data suggest that the ground state involves shortrange magnetic order, which is frustrated by the coexistence/ competition of FM and AFM correlations, together with the characteristic geometric frustration of the kagom e lattice. Magnetic susceptibility data rule out a spin-glass state, pointing to an exotic ground state comparable to the spin-ice or spin-liquid states. This makes YCa 3 (VO) 3 (BO 3 ) 4 one of the most highly frustrated experimental realizations of the kagom e lattice yet discovered.

Frustrated Ground State. -The new title compound is synthesized by reaction of Y2O3, CaCO3, V2O5, and B2O3 (flowing 3.5% H2/Ar, 1000°C, 7 d). The compound is characterized by single crystal neutron and X-ray diffraction, powder neutron diffraction, and magnetic susceptibility and magnetization measurements. YCa3(VO)3(BO3)4 crystallizes with a gaudefroyite-type structure in the hexagonal space group P3 (Z = 1) and exhibits a new supercell driven by the ordering of columns of isolated triangular ions. The magnetic exchange in the title compound is dominated by antiferromagnetic correlations along one-dimensional chains of edge-sharing VO6 octahedra at high temperatures, with ferromagnetic interactions appearing at low temperatures. The coexistence of ferromagnetic and antiferromagnetic correlations, together with geometric frustration, results in a highly frustrated magnetic ground state. Thus YCa 3 (VO) 3 (BO 3 ) 4 is one of the most highly magnetically frustrated experimental realization of the Kagome lattice. -(MIILER, W.; CHRISTENSEN, M.; KHAN, A.; SHARMA, N.; MACQUART, R. B.; AVDEEV, M.; MCINTYRE, G. J.; PILTZ, R. O.; LING*, C. D.; Chem. Mater. 23 (2011) 5, 1315-1322, http://dx.