Syntheses and Characterization of Nine Quaternary Uranium Chalcogenides Among the Compounds A2M3UQ6 (A = K, Rb, Cs; M = Pd, Pt; Q = S, Se)

Nine compounds from the series A2M3UQ6 (A = K or Rb or Cs; M = Pd or Pt; Q = S or Se) were synthesized by reacting U, M, and Q in ACl or A2Qx fluxes. These compounds crystallize with eight formula units in the NaBa2Cu3O6 structure type, in space group Fmmm of the orthorhombic system. The structure contains hexagons formed from six edge-sharing square-planar coordinated M atoms, which in turn edge-share with trigonal-prismatically coordinated U atoms, forming layers along (010). These layers are separated by A atoms. Electrical resistivity measurements along the [100] direction of Rb2Pd3US6 show typical semiconductor behavior. Magnetic susceptibility measurements on Rb2Pd3US6 display marked magnetic anisotropy and unusually low magnetic moments owing to crystalline electric field effects.