Pd/Cu Site Interchange and Non-Fermi-Liquid Behavior inUCu4Pd

X-ray-absorption fine-structure measurements of the local structure in ${\mathrm{UCu}}_4\mathrm{Pd}$ are described which indicate a probable lattice-disorder origin for non-Fermi-liquid behavior in this material. Short Pd-Cu distances are observed, consistent with $(24\pm 3)\%$ of the Pd atoms occupying nominally Cu sites. A “Kondo disorder” model, based on the effect on the local Kondo temperature $T_K$ of this interchange and some additional bond-length disorder, agrees quantitatively with previous experimental susceptibility data, and therefore also with specific heat and magnetic resonance experiments.