Crystal structure and electronic properties of the new compound U3Fe4Ge4

The new ternary compound U 3 Fe 4 Ge 4 was prepared by melting the pure metals in the stoichiometric ratio. An ingot of large scale domain was obtained by decreasing the temperature from the liquid state down to 1000 °C over 4 h. Single crystal X-ray diffraction revealed that U 3 Fe 4 Ge 4 crystallizes with the Gd 3 Cu 4 Ge 4 -type of structure, in the orthorhombic space group Immm (no. 71), Z = 2, with unit-cell parameters at room temperature of, a = 4.090(1) A, b = 6.639(1) A and c = 13.702(1) A. The crystal structure is characterized by two U, one Fe and two Ge independent crystallographic positions and can be described as resulting from the condensation by face-sharing and edge-sharing of U(1)Ge6 octahedrons, U(2)Ge6 trigonal prisms and Fe(1)Ge4 tetrahedrons. The electronic properties of this new compound were investigated by means of electrical resistivity, thermopower, ac and dc magnetic susceptibility and 57 Fe Mossbauer spectroscopy. U 3 Fe 4 Ge 4 undergoes a ferromagnetic transition below T C = 17(1) K. The low temperature (4 K) 57 Fe Mossbauer spectra can be well fitted using a model with Fe atoms in a paramagnetic state, suggesting that the magnetic ordering originates from the U sublattice alone.