Structural and Physical Properties of the Heavy Fermion Metal Ce$_2$NiAl$_6$Si$_5$

TL;DR

This study introduces Ce$_2$NiAl$_6$Si$_5$, a layered heavy fermion metal near a quantum critical point, revealing complex magnetic and electronic behaviors driven by strong electron correlations.

Contribution

The paper reports the synthesis, structural characterization, and physical properties of a new Ce-based heavy fermion compound with evidence of quantum criticality.

Findings

Layered tetragonal structure with Ce square nets

Low Sommerfeld coefficient indicating Kondo interactions

Signs of magnetic ordering or correlations below 0.6 K

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 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$_2$NiAl$_6$Si$_5$, 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$_2$NiAl$_6$Si$_5$ is a layered heavy fermion metal, naturally located in proximity to a spin-density-wave quantum critical point.