Unusual non-fermi liquid behavior of Ce1-xLaxNi9Ge4Ce1-xLaxNi9Ge4 analyzed in a single impurity Anderson model with crystal field effects

CeNi9Ge4CeNi9Ge4 exhibits unusual non-Fermi liquid behavior with the largest ever recorded value of the electronic specific heat ΔC/T≅5.5JK-2mol-1 without showing any evidence of magnetic order. Specific heat measurements show that the logarithmic increase of the Sommerfeld coefficient flattens off below 200 mK. In marked contrast, the local susceptibility ΔχΔχ levels off well above 200 mK and already becomes constant below 1 K. Furthermore, the entropy reaches 2Rln2 below 20 K corresponding to a four-level system. An analysis of C and χχ was performed in terms of an SU(N=4)SU(N=4) single impurity Anderson model with additional crystal electric field (CEF) splitting. Numerical renormalization group calculations point to a possible consistent description of the different low-temperature scales in ΔcΔc and ΔχΔχ stemming from the interplay of Kondo effect and crystal field splitting.