Tm4IrIn and Lu4PtIn - In-4 tetrahedra embedded in RE22 polyhedra

The rare earth-rich indides Tm4IrIn and Lu4PtIn were synthesized by reaction of the elements in sealed tantalum ampules in an induction furnace. Tm4IrIn (a = 1340.77(4) pm) and Lu4PtIn (a = 1338.0(1) pm) crystallize with the Gd4RhIn-type structure, space group F (4) over bar 3m. The Lu4PtIn structure was refined from single crystal X-ray diffractometer data: wR = 0.0524, 517 F-2 values and 20 variables. The striking crystal chemical motif is the fcc packing of In 4 tetrahedra with 318 pm In-In. The Lu4PtIn structure is closely related to the structures of Lu13Ni6In, Lu14Pd3In3 and Lu20Ir5In3 which all show icosahedral indium coordination and different condensation patterns that build up the indium substructure that consists of a dumbbell in Lu14Pd3In3 and a triangle in Lu20Ir5In3. The results of magnetic susceptibility measurements indicate Curie-Weiss paramagnetism for Tm4IrIn (7.76(1) mu(B) per thulium atom) without magnetic ordering down to 2.5 K. Lu4PtIn is Pauli-paramagnetic.