Low-temperature specific heat for off- and near-stoichiometric UAsSe

Two UAsSe single crystals with slight variations of the As/Se content ratio have been investigated. The development of the low-T upturn in the resistivity is accompanied by smooth decrease of the Curie temperature. The sample with TC=116.9 K and almost invisible upturn could be regarded as a near-stoichiometric, slightly disordered one, whereas the specimen with TC=101.5 K appears to be an off-stoichiometric, more strongly disordered one. Clear differences between both electronic and lattice contributions to the specific heat for off- and near-stoichiometric UAsSe crystals have also been found. We ascribe the smaller low-T specific heat for the off-stoichiometric sample in comparison to the near-stoichiometric one to a weaker hybridization between 5f and conduction-electron states accompanied by the relative shift of 5f band with regard to EF.