Structural anomaly and crystalline electric field excitations in low-dimensional KU2Te6

Layered ternary actinide chalcogenides contain unique structural and magnetic properties that remain underexplored. KU2Te6 is a new member of the A-R-Q (A= alkali; R= actinide; Q= chalcogenide) materials family crystallizing in the Cmcm space group as part of the CsTh2Te6 structure type. Evidence of a structural anomaly appears near Ts=48 K as a weak feature in specific heat and electrical resistivity. Magnetism in this material derives from local non-Kramers U4+ ions as suggested by charge balance and crystalline electric-field susceptibility analysis. These ions form one-dimensional U-U chains along the a axis, but do not exhibit signs of magnetic order to T=0.36 K. The absence of magnetic order is consistent with the crystalline electric-field splitting of the U4+ J=4 manifold into a series of nondegenerate singlets.