Non-Fermi-liquid instabilities in non-centrosymmetric heavy-fermion CePtSi: A low-temperature study

CePtSi is a known heavy-fermion compound with no magnetic ordering. It forms in a tetragonal non-centrosymmetric crystal structure. Pronounced Kondo features at elevated temperatures originate from magnetic Ce⁺³ ions. Towards low temperatures coherence develops in the electronic scattering and a Kondo lattice forms below 30K. At the same temperature scale the electronic specific heat steeply escalates to C_P/T≃0.7Jmol^-1K^-2. Considerable effort has been devoted in previous studies to find the origin for the observed low-temperature divergences in thermal properties in CePtSi and in particular for the putative non-Fermi-liquid behaviour. To date however, a coherent description of the physics of CePtSi remains to be found. In this work we present low-temperature results of χ(T), C_P(T), and ρ(T). A picture of the low-temperature nature of this compound is forwarded that is consistent across the thermal properties. We illustrate how a non-Fermi-liquid state intervenes between the high-temperature incoherent Kondo region and Kondo lattice ground state of CePtSi. The non-Fermi-liquid region effectively mediates a crossover from the high-temperature paramagnetic state in CePtSi to its Fermi-liquid ground state. We argue that magnetic ordering is avoided through a small but intrinsic dissimilarity between nearest-neighbour Ce atoms.