SINGLE URANIUM-SITE PROPERTIES OF THE DILUTE HEAVY-ELECTRON SYSTEM UXTH1-XRU2SI2 (X-LESS-THAN-OR-EQUAL-TO-0.07)

Specific heat C, electrical resistivity rho, magnetization M and magnetic susceptibility chi have been measured for the dilute tetragonal heavy-electron compounds UxTh1-xRu2Si2 (x less-than-or-equal-to 0.07), in the temperature range 100 mK less-than-or-equal-to T less-than-or-equal-to 360K and in the magnetic fields H up to 55 kOe. Non-Fermi-liquid behavior with unusual In T dependence of C, rho and chi has been observed at the low temperatures: as the temperature is lowered below about 10 K, C/T and chi increase logarithmically, and rho decreases logarithmically. Systematical variations of these quantities with uranium concentration indicate that the observed non-Fermi-liquid behavior is ascribed to the properties of a single U ion embedded in the Th site of the ThRu2Si2 metal. The magnetization curves M vs H/T indicate a strong uniaxial magnetic anisotropy along the tetragonal c-axis as well as a strong reduction of the 5f moment of U ions. A possible interpretation based on the recent developments of the S = 1/2 two-channel Kondo model is given.