Coherent electronic scattering in orbital-Kondo ferromagnet UAs1−xSe1+x

Abstract 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 UAs 1− x Se 1+ 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.