Abstrakt
Uranium Laves phase UTi2 does not exist in a pure form, but can be stabilised by the presence of hydrogen, which can be absorbed in concentration exceeding 5 H atoms/f.u. Low temperature specific heat, magnetic susceptibility, and resistivity indicate that UTi2H5 is a spin fluctuator close to the verge of magnetic ordering.
Its susceptibility follows at high temperatures the Curie-Weiss law with U effective moment mu(eff[) = 3.1 mu(B)/U and paramagnetic Curie temperature Theta(p) = -200 K. The temperature dependence of specific heat exhibits a pronounced and weakly field dependent upturn in C-p/T versus T below 10 K reflecting the effect of spin fluctuations.
It can be described by an additional T-1/2 term. The Sommerfeld coefficient gamma = 256 mJ/mol K-2 classifies the compound as a mid-weight heavy fermion.
Spin fluctuations are affecting also electrical and thermal transport and thermoelectric power, which all resemble UAl2. A lattice anomaly at approximate to 240 K, attributed to the melting of hydrogen sublattice, reflects in most of bulk properties.