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Single crystals of UP1.8As0.2, UAsS and UAs 1− xSe1 + x, solid solutions (0 ≤ x ≤ 0.06) were grown by the chemical vapour transport method and their temperature-dependent resistivity and magnetoresistivity, at 4.2 K in fields up to 14 T, have been examined. Their residual resistivity increases from ϱ(4.2 K)/ϱ(TM) = 0.22 (ϱ(TM) is the resistivity at the magnetic phase transition temperature) through 0.51 to 0.94 for x = 0 and to 1.17 for x = 0.06, for the first, second and third system, respectively. The electron transport properties are considered as indicating an impurity origin of the Kondo-Iike temperature-dependent component of the total resistivity of the UAsSe ferromagnet. Examination of UAsSe single crystals by means of high-resolution transmission electron microscopy and X-ray and neutron diffraction revealed a well-ordered crystal structure with possible, partial occupation (less than 20%) of Se at As sites and vice versa. Moreover, an anomalously large anisotropy of the Debye- Waller factor for As in UAsSe has been found. |
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