LAUSR

A series of A2M4U6S17 (A = alkali metal; M = Pd, Pt) compounds, specifically K2Pd4U6S17, K2Pt4U6S17, Rb2Pt4U6S17, and Cs2Pt4U6S17, were synthesized using the combined boron-chalcogen mixture and molten flux crystal growth methods. The formation of rubidium- and cesium-containing analogues resulted from a in situ alkali polysulfide flux formed from alkali carbonates. The successful synthesis of single crystals of the title compounds allowed for their structural characterization by single-crystal X-ray diffraction. The structure determination revealed disorder of the alkali cations in Rb2Pt4U6S17 and Cs2Pt4U6S17, while the potassium cations in K2Pd4U6S17 and K2Pt4U6S17 were fully ordered. Magnetic measurements were performed on samples of K2Pt4U6S17, Rb2Pt4U6S17, and Cs2Pt4U6S17 that contained small amounts of paramagnetic β-US2 and diamagnetic PtS. Antiferromagnetic order was observed at TN = 9.1 K for K2Pt4U6S17. No long-range magnetic order was observed for Rb2Pt4U6S17 and Cs2Pt4U6S17. Uranium moments of 2.5, 2.6, and 2.6 μB were measured for K2Pt4U6S17, Rb2Pt4U6S17, and Cs2Pt4U6S17, respectively.