Novel Canonical Heavy Fermion Compound

The field of heavy fermion physics emerged nearly four decades ago and has since become one of the central research directions of condensed matter physics. While significant progress has been made in understanding heavy fermion behavior and accompanying phenomena, the global trends still remain unclear. One of the avenues in the search for heavy fermions has focused on compounds with high coordination, and, therefore, low concentration of uranium atoms. This approach has proven fruitful in the case of antiferromagnetic U₂Zn₁₇ and UCd₁₁, as well as unconventional superconductor UBe₁₃. The two former compounds are also the only two canonical heavy fermions. In this work, we present the discovery of the third canonical heavy fermion U₁₁Hg₄₅. This compound exhibits an antiferromagnetic transition at T_N = 2 K, which can be suppressed by application of magnetic field. A high value of the Sommerfeld coefficient γ = 0.6 J/U mol K² is likely related to the itineracy of the f-electrons, as evidenced by the high value of the Rhodes-Wohlfarth ratio along with the small entropy of the antiferromagnetic transition.