ThAsSe diamagnet: Evidence for a Kondo effect derived from structural two-level systems

We report a study of an anomalous scattering mechanism in the structurally disordered diamagnet ThAsSe. Below 20 K, its electrical resistance displays a logarithmic correction over one decade in temperature, which is affected by neither strong magnetic fields (Bless than or equal to17 T) nor high hydrostatic pressures (pless than or equal to1.88 GPa). Dynamic disorder in the ThAsSe single crystals is reflected by, e.g., a quasilinear-in-T term of nonelectronic origin in the specific heat at Tless than or similar to1.7 K. The ln T dependence of the resistance is interpreted as being due to the interaction of the conduction electrons with movable structural defects.