Structural and physical properties of the U9Fe7Ge24 uranium germanide

A new ternary compound, U9Fe7Ge24, was synthesized by arc-melting the elements, followed by annealing at 900 °C. This compound was characterized by single crystal and powder X-ray diffraction, magnetization, specific heat and electrical transport measurements. It crystallizes in an original tetragonal structure type (space group I4/mmm), with lattice parameters a = 12.3789(2) Å and c = 18.2881(3) Å. Three uranium, eighth germanium, and three iron crystallographic sites exist in this structure, with the atoms making a stacking of infinite chains along the a and b axis. From their interatomic distances strong interactions between the uranium and germanium atoms can be predicted. The magnetic and specific heat measurements down to 2 K do not show any magnetic transition. The Curie–Weiss behaviour with a negative paramagnetic Curie temperature θp = −94 K and reduced effective magnetic moment of μeff = 2.13 μB/U indicate that the compound is rather far from onset of magnetism, presumably due to a strong hybridisation of the 5f and ligand states. The electrical transport measurements show a metallic behaviour.

► U9Fe7Ge24 is a new ternary intermetallic compound (50).
► It crystallizes in an original tetragonal structure type (57).
► It shows paramagnetic behaviour in the 2 K < T < 300 K temperature range.
► Has a low effective magnetic moment and a small Sommerfeld coefficient (81).
► It behaves as a metal concerning the electrical properties (55).