LAUSR

Abstract U 3 Si 2 reversibly absorbs hydrogen at very low H 2 pressures (kPa range), yielding U 3 Si 2 H 1.8 . One characteristic desorption temperature implies that there is only one type of H sites. U 3 Si 2 is a weak Pauli paramagnet ( χ −8  m 3 /mol U) with the shortest inter-uranium distances between the U atoms in different sheets ( d U-U  = 332 pm). The volume-expanded (10%) hydride is a spin fluctuator with temperature dependent magnetic susceptibility and a weak ferromagnetic component gradually arising below T  = 100 K. The location of U 3 Si 2 H 1.8 at the verge of magnetic ordering is evidenced by the low temperature specific heat with an upturn in C / T and a dramatic enhancement of the Sommerfeld coefficient of electronic specific heat γ , which reaches 500 mJ/mol f.u. K 2 .