Pt atoms adsorbed onto Ge(001) surface form extremely well-ordered nanowire arrays by self-organization after high-temperature annealing. Using scanning tunneling spectroscopy/microscopy, it is shown that they are metallic and defect free. They are only 0.4 nm thick with a spacing of 1.6 nm in between, and have aspect ratios up to 1000. Their formation can be discussed in terms of a relativistic property possessed by heaviest 5d elements, and the pathway to their formation can be explained by dimer breakup on Ge(001) surface at elevated temperatures followed by a surface polymerization reaction. (C) 2003 American Institute of Physics.