Crossover from single ion to coherent non-Fermi liquid behavior in Ce1-xLaxNi9Ge4Ce1-xLaxNi9Ge4

We report specific heat and magneto-resistance studies on the compound Ce1-x1-xLaxxNi99Ge44 for various concentrations over the entire stoichiometric range. Our data reveal single-ion scaling with Ce-concentration between x=0.1x=0.1 and 0.950.95. Furthermore, CeNi99Ge44 turns out to have the largest ever recorded value of the electronic specific heat Δc/T≈Δc/T≈ 5.5 J K-2mol-1 at T=0.08T=0.08 K which was found in Cerium f-electron lattice systems. In the doped samples Δc/TΔc/T increases logarithmically in the temperature range between 3 K and 50 mK typical for non-Fermi liquid (nFl) behavior, while ρρ exhibits a Kondo-like minimum around 30 K, followed by a single-ion local nFl behavior. In contrast to this, CeNi99Ge44 flattens out in Δc/TΔc/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 Ce1-x1-xLaxxNi99Ge44 a unique system on the borderline between Fermi liquid and nFl physics.