Direct Fermi-surface image of hidden nesting for NaMo{sub 6}O{sub 17} and KMo{sub 6}O{sub 17}

We report direct Fermi-surface images obtained with angle-resolved photoemission spectroscopy (ARPES) for NaMo{sub 6}O{sub 17} and KMo{sub 6}O{sub 17} above the charge-density wave transition temperatures. We also report ARPES spectra of the valence band of NaMo{sub 6}O{sub 17}. The images imply a Fermi surface (FS) based on three underlying quasi-one-dimensional (quasi-1D) surfaces. Thus it agrees in detail with that expected in the hidden nesting picture of Whangbo {ital et al.} [Science {bold 252}, 96 (1991)], but differs greatly from a FS deduced in a previous study by Breuer {ital et al.} [Phys. Rev. Lett. {bold 76}, 3172 (1996)], which found only two underlying quasi-1D surfaces. {copyright} {ital 1997} {ital The American Physical Society}