On the crystal structure and physical properties of the UFeSb2 compound

The UFeSb2 ternary uranium antimonide has been prepared by arc-melting, followed by annealing at 750 °C for 1 week, and was characterized by means of powder X-ray diffraction, electrical resistivity, magnetization, Mössbauer spectroscopy and specific heat measurements. UFeSb2 crystallizes in the tetragonal HfCuSi2-type structure (space group P4/nmm, a = 0.43249(3) nm, c = 0.90962(7) nm), with the U, Fe and Sb atoms at the positions of Hf (2c), Cu (2b) and Si (2a and 2c), respectively. The nearest neighbor atoms of U are at distances close to or higher than the metallic radii sum, pointing to the possibility of a non negligible U magnetic moment, which contrasts with the very short Fe-Sb1 distances that indicate a probable collapse of Fe magnetic moments. The UFeSb2 undergoes a ferromagnetic-type transition at 31(1) K with a small saturation magnetization, suggesting for this compound a non-negligible U hybridization, itinerant magnetism and/or a complex magnetic structure. Mössbauer spectroscopy confirms that the magnetism is ruled by the U sub-lattice, with neither long-range magnetic ordering nor standard spin-glass behavior of the iron sub-lattice. The Sommerfeld coefficient of the electronic specific heat is γ = 51(1) mJ/mol K2, which classifies this compound as a medium correlated system.