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A.M. thanks Eusko Jaurlaritza for financial support.The electronic structure of Pb/Ge(111) has been probed along the temperature-induced phase transition ct -root 3X root 3R30 degrees double right arrow 3 X 3 using angle-resolved photoemission. The alpha-root 3X root 3R30 degrees phase is metallic due to the existence of a half-filled, dispersing surface band. The 3 X 3 phase is characterized by the appearance of an additional surface band with 3 X 3 periodicity, whose role in the phase transition is discussed. The Fermi-surface topology of the alpha-root 3X root 3R30 degrees phase has been probed using angle-resolved photoemission. Its shape is undulated, and it resembles strongly the theoretical prediction, with a Fermi momentum of 0.31 Angstrom(-1) along <(Gamma K)over bar> directions and 0.40 Angstrom(-1) along <(Gamma M)over bar> directions. These values were determined from different experimental methods, and agree with the values needed for a perfect 3 X 3 nesting. However, the Fermi surface exhibits no large flat areas suitable for electronic nesting.engjournal articlehttp://dx.doi.org/10.1103/PhysRevB.57.14758http://journals.aps.orgopen access538.9Charge-Density waveAngle-Resolved photoemissionGe(111) SurfacesPbPhaseW(001)ReconstructionsSpectroscopyInterfacesSystemsFísica de materiales