Structural and physical properties of the heavy fermion metal Ce₂NiAl₆Si₅

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 advances in both experiments and theory. In this work, we report the structural and physical properties of a new quaternary Ce-based heavy fermion compound, Ce_2NiAl_6Si_5, synthesized using 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 K^2, with a reduced entropy indicative of significant Kondo interactions. Below 0.6 K, an upturn 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 specific heat around 0.4 K. These results suggest that Ce_2NiAl_6Si_5 is a layered heavy fermion metal, naturally located in proximity to a spin-density-wave quantum critical point.