Coherent electronic scattering in orbital-Kondo ferromagnet UAs1-x Se1+x

We have examined an influence of the As-Se chemical composition on the low-T upturn of resistivity ρ(T) (below ∼50 K) and the peak contribution (at ∼30 K) to thermoelectric power S(T), both due to the orbital Kondo (OK) effect, in UAs1-x Se1+x ferromagnet (T C between 85 and 117 K). The ρ(T) upturn decreases monotonously with x decreasing below 0.074 and vanishes leaving behind ferromagnetic metal-like ρ(T) behaviour for crystals with the lowest x examined. At the same time the peak contribution to S(T) vanishes, too. Both the ρ(T) upturn and the peak contribution to S(T) are reduced for x>0.074. The role of Se excess in a formation of two-level systems in uranium arsenoselenide is discussed