Characterization of the novel intermetallic compounds U2Co3Ge, U6Co12Ge4 and U6Co12Ge4C

The new ternary compounds U2Co3Ge and U6Co12Ge4 have been discovered during the investigation of the U–Co–Ge system. The Laves phase, U2Co3Ge crystallizes in the hexagonal Mg2Cu3Si type structure (P63/mmc) with the lattice parameters a = 5.203(1) Å and c = 7.687(1) Å. U6Co12Ge4 and its carbon-inserted derivative U6Co12Ge4C, crystallize, at room temperature in cubic unit cells, which derive from the Ca3Ag8 type structure (Im3¯m space group) with the lattice parameter a = 8.690(1) Å and a = 8.740(1) Å, respectively. An interesting feature of their crystal structure is the formation of [U6] octahedra, which can be either empty or occupied by light elements such as O, N, or C. Measurements of the physical properties revealed that U2Co3Ge and U6Co12Ge4 are Pauli paramagnets with metallic character of their electrical conductivity. In turn, U6Co12Ge4C showed Curie–Weiss paramagnetism with an effective magnetic moment of 2.3(1)μB per U atom.

Research highlights
► Phase relationships in the U–Co–Ge ternary system.
► New compounds in the Co-rich corner.
► Quaternary inserted C derivative.
► Pauli paramagnetism and normal metallic electrical conduction.
► Strong hybridization 5f/3d wave-functions.