Kondo-lattice formation in cubic-phase YbCu5

The YbCu5 phase with C15b structure has been prepared by a high-pressure technique, and its physical properties have been investigated. The temperature dependence of magnetic susceptibility, electrical resistivity, and specific heat show Kondo-lattice formation. Furthermore, a heavy Fermi-liquid state without magnetic ordering down to 2.0 K is found to evolve below about 6 K. The electronic specific heat coefficient γ is enhanced to values as large as to 550 mJ/molK2. The magnetization measured up to 40 T at 1.6 K has a field dependence which is expected for a Kondo system when the total angular momentum is J>1. All results are in good agreement with the extrapolation of the previous results of YbCu5-xAgx (0.125≤x≤1.0) for x→0. The concentration dependence of characteristic temperatures of YbCu5-xAgx can be quantitatively explained by the chemical pressure effect within the compressible Kondo model for the full range of Ag concentration ( 0.0≤x≤1.0). The origins of Kondo-lattice formation in YbCu4Ag and the valence transition in YbCu4In are discussed. copyright 1997 The American Physical Society