Electronic structure of $R\mathrm{Au}\mathrm{Sn}$ ($R=\mathrm{Sc}$, Ce, Gd, Er, and Lu) investigated with x-ray photoelectron spectroscopy and band structure calculations

We have investigated the electronic structure of the intermetallic compounds ScAuSn, CeAuSn, GdAuSn, ErAuSn, and LuAuSn using x-ray photoelectron spectroscopy and band structure calculations. We find good general agreement between the experimental and calculated valence band spectra, provided that the spin-orbit interaction in the Au bands as well as correlation effects in the open rare-earth $4f$ shell are included in the calculations. The rare-earth $4f$ and $\mathrm{Au}5d$ have well identified spectral features far away from the Fermi level. The spectral weight in the vicinity of the Fermi level is built up of mainly $\mathrm{Au}∕\mathrm{Sn}$ $sp$ and rare-earth $spd$ bands. We find an extremely low or vanishing spectral weight at the Fermi level for ScAuSn and LuAuSn, consistent with their semiconducting behavior as revealed by temperature dependent resistivity measurements.

Figure 1

Crystal structure of the intermetallic compounds $R\mathrm{Au}\mathrm{Sn}$. On the left-hand side, the cubic MgAgAs type and on the right-hand side, the hexagonal NdPtSb type are drawn.

Figure 2

(Color online) Experimental valence band photoemission spectra and calculated valence band density of states of the hexagonal compounds CeAuSn, GdAuSn, and ErAuSn (left panels) and of the cubic compounds ScAuSn and LuAuSn (right panels). A Gaussian broadening of $0.5–0.7\mathrm{eV}$ has been included in the calculated density of states.

Figure 3

(Color online) Experimental (top panel) and calculated (bottom panel) $\mathrm{Au}4f$ core-level photoemission spectra of Au metal, the hexagonal compounds CeAuSn, GdAuSn, and ErAuSn, as well as the cubic compounds ScAuSn and LuAuSn.

Figure 4

(Color online) Close-up of the experimental photoemission spectra (top panel) in the vicinity of the Fermi level together with the calculated density of states (bottom panel).

Figure 5

(Color online) Temperature dependence of the resistivity of cubic ScAuSn and LuAuSn and hexagonal GdAuSn and ErAuSn.