Low-temperature ultrahigh-resolution photoemission (PE) spectroscopy of the recently discovered binary icosahedral (i) ${\mathrm{Cd}}_{5.7}\mathrm{Yb}$ and its 1/1-cubic approximant Cd${}_6$Yb has commonly revealed a sharp Fermi edge with a marked spectral intensity decrease towards the Fermi level ${(E}_F),$ indicating the presence of a dip near $E_F$ which is consistent with the recent result of electronic structure calculations [Y. Ishii and T. Fujiwara, Phys. Rev. Lett. 87, 206408 (2001)], and the dip at $E_F$ is found to be much deeper in $i-{\mathrm{Cd}}_{5.7}\mathrm{Yb}$ than in $1/1-{\mathrm{Cd}}_6\mathrm{Yb}.$ Moreover, surface core-level shifts (SCS’s) are clearly observed in the quasicrystal and the approximant, and the SCS’s are found to be substantially different between these two compounds of different long-range orders.

• Received 11 February 2002

DOI:https://doi.org/10.1103/PhysRevB.65.224207