Fermi-level tuning inY1−xUxPd3

The $5f$-electron photoemission peak 1 eV below the Fermi energy $E_F$ in U${\mathrm{Pd}}_3$ is generally assigned as a $5f^2\to 5f^1$ transition, consistent with other evidence of a stable ${\mathrm{U}}^{4+}$ valence state. We report resonant photoemission spectra for the system ${\mathrm{Y}}_{1-x}{\mathrm{U}}_x{\mathrm{Pd}}_3$ which show that the peak narrows and shifts to the Fermi level as $x$ decreases from 1. We hypothesize that the shift arises from a decrease in the Fermi energy as ${\mathrm{Y}}^{3+}$ replaces ${\mathrm{U}}^{4+}$, and therefore expect interesting changes in transport properties as $E_F$ is tuned in this way.