X-ray absorption fine structure and field-dependent specific heat measurements of non-Fermi liquid ${\mathrm{U}}_3{\mathrm{Ni}}_3{\mathrm{Sn}}_4$

Although most known non-Fermi-liquid (NFL) materials are structurally or chemically disordered, the role of this disorder remains unclear. In particular, very few systems have been discovered that may be stoichiometric and well ordered. To test whether ${\mathrm{U}}_3{\mathrm{Ni}}_3{\mathrm{Sn}}_4$ belongs in this latter class, we present measurements of the x-ray absorption fine structure of polycrystalline and single-crystal ${\mathrm{U}}_3{\mathrm{Ni}}_3{\mathrm{Sn}}_4$ samples that are consistent with no measurable local structural disorder. We also present temperature-dependent specific heat data in applied magnetic fields as high as 8 T that show features that are inconsistent with the antiferromagnetic Griffiths’ phase model, but do support the conclusion that a Fermi-liquid/NFL crossover temperature increases with applied field. These results are inconsistent with theoretical explanations that require strong disorder effects, but do support the view that ${\mathrm{U}}_3{\mathrm{Ni}}_3{\mathrm{Sn}}_4$ is a stoichiometric, ordered material that exhibits NFL behavior, and is best described as being near an antiferromagnetic quantum critical point.