Magnetic anisotropy in the UxTh1−xZn8.5 system

We have investigated the source of the anisotropic susceptibility of UZn8.5 by preparing single crystals of UxTh1–xZn8.5 for small x. Preliminary indications are that anisotropic exchange, rather than crystal field effects, are responsible for the anisotropy, but possible impurity contributions to the (anisotropic) susceptibility of the ThZn8.5 do not permit a stronger statement. Further measurements for small x show that both the electronic specific heat and the susceptibility at low temperature are strongly enhanced, and that Kondo-type resistivity minima are observed. The enhancements are somewhat reduced in the concentrated system UZn8.5.