Low-temperature annealing of the cleaved Si(111)-(2 x 1) surface revealed the existence of an intrinsic 5 x 5 reconstruction on the clean Si(111) surface. The electronic structure of the Si(111)-(5 x 5) surface, obtained with angle-resolved photoemission, was almost identical to that of the 7 x 7 reconstruction. This was strong evidence that the 5 x 5 reconstruction was also of the dimer–adatom stacking-fault type. The experimental observation of a 5 x 5 reconstruction supports theoretical results that the 7 x 7 and 5 x 5 dimer–adatom–stacking-fault models were very close in total surface energy. Observation of an Intrinsic 5 x 5 Reconstruction on the Clean Si(111) Surface. R.I.G.Uhrberg, E.Landemark, L.S.O.Johansson: Physical Review B, 1989, 39, 13525-8