Crossover from single ion to coherent non-Fermi liquid behavior in [formula omitted

Abstract

We report specific heat and magneto-resistance studies on the compound Ce 1 - x La x Ni 9 Ge 4 for various concentrations over the entire stoichiometric range. Our data reveal single-ion scaling with Ce-concentration between x = 0.1 and 0.95 . Furthermore, CeNi 9 Ge 4 turns out to have the largest ever recorded value of the electronic specific heat Δ c / T ≈ 5.5 J K - 2 mol - 1 at T = 0.08 K which was found in Cerium f-electron lattice systems. In the doped samples Δ c / T increases logarithmically in the temperature range between 3 K and 50 mK typical for non-Fermi liquid (nFl) behavior, while ρ exhibits a Kondo-like minimum around 30 K, followed by a single-ion local nFl behavior. In contrast to this, CeNi 9 Ge 4 flattens out in Δ c / T below 300 mK and displays a pronounced maximum in the resistivity curve at 1.5 K indicating a coherent heavy fermion groundstate. These properties render the compound Ce 1 - x La x Ni 9 Ge 4 a unique system on the borderline between Fermi liquid and nFl physics.