UHg_{3} - A Heavy Fermion Antiferromagnet Similar to U_{2}Zn_{17} and   UCd_{11}
  Heavy Fermion physics deals with the ground state formation and interactions in f-electron materials where the electron effective masses are extremely large, more than 100 times the rest mass of an electron. The details of how the f-electrons correlate at low temperature to become so massive lacks a coherent theory, partially because so few materials display this heavy behavior and thus global trends remain unclear. UHg_{3} is now found experimentally to be a heavy Fermion antiferromagnet, just as are all the other U_{x}M_{y} compounds with the metal M being in column II B (filled d electron shells) in the periodic table (Zn/Cd/Hg) and the spacing between Uranium ions being greater than the Hill limit of 3.5 Angstroms. This result that, independent of the structure of these U_{x}M_{y}, M=Zn/Cd/Hg, compounds and independent of the value of their Uranium Uranium spacings (ranging from 4.39 to 6.56 Angstroms), all exhibit heavy Fermion antiferromagnetism, is a clear narrowing of the parameters important for understanding the formation of this ground state. The sequence of antiferromagnetic transition temperatures, T_{Neel}, of 9.7 K, 5.0 K, and 2.6 K for U_{x}M_{y} as the metal M varies down column II B (Zn/Cd/Hg) indicates an interesting regularity for the antiferromagnetic coupling strength. 
J. S. Kim and G. R. Stewart
cond-mat.str-el