We have examined the electronic structure of the heavy fermion ${\mathrm{Yb}}_2{\mathrm{Pd}}_2\mathrm{Sn}$ in comparison with the superconductor ${\mathrm{YbPd}}_2\mathrm{Sn}$ by means of high-resolution photoelectron spectroscopy (PES) and resonant x-ray emission spectroscopy (RXES). The PES data are interpreted in light of the density of states calculated within the local density approximation plus the dynamical mean-field theory. Our analysis of the RXES data shows that the valence of Yb in ${\mathrm{Yb}}_2{\mathrm{Pd}}_2\mathrm{Sn}$ is weakly fluctuating, indicating weak but finite $c–f$ hybridization, and decreases slightly with temperature. In contrast, the Yb valence in ${\mathrm{YbPd}}_2\mathrm{Sn}$ is nearly 3$+$ and does not show any temperature dependence, suggesting that the Yb $4f$ electrons are localized and the superconductivity is due to the Pd conduction electrons. The constant initial state spectra at the Yb $4d–4f$ resonance for ${\mathrm{Yb}}_2{\mathrm{Pd}}_2\mathrm{Sn}$ clearly show resonant behavior for ${\mathrm{Yb}}^{3+}$ and antiresonance for ${\mathrm{Yb}}^{2+}$, indicating that the ${\mathrm{Yb}}^{3+}$ and ${\mathrm{Yb}}^{2+}$ states are intimately correlated.

• Received 6 June 2012

DOI:https://doi.org/10.1103/PhysRevB.86.085137