Structural and Physical Properties of the Heavy Fermion Metal Ce₂NiAl₆Si₅

Abstract Strongly correlated electrons at the verge of quantum criticality give rise to unconventional phases of matter and behaviors, with the discovery of new quantum-critical materials driving synergistic experimental and theoretical advances. In this paper, we report the structural and physical properties of a new quaternary Ce-based heavy fermion compound, Ce₂NiAl₆Si₅, which was synthesized via the self-flux method. This compound forms a layered tetragonal structure (space group P4/nmm) with square nets of Ce atoms separated by Si-Al or Ni-Si-Ge layers. Specific heat measurements show a low-temperature Sommerfeld coefficient of 1.4 J/mol-Ce⋅K² with reduced entropy, indicative of significant Kondo interactions. Below 0.6 K, an increase in resistivity and a deviation in magnetic susceptibility suggest the appearance of magnetic ordering or the development of dynamic magnetic correlations, which is further supported by a bulge in the specific heat around 0.4 K. The findings of this study suggest that Ce₂NiAl₆Si₅ is a layered heavy fermion metal naturally located near a spin-density-wave quantum critical point.