Initial Ag adsorption on Si(5 5 12)-2 × 1 and its parasitic Si(7 7 17)-2 × 1

•The initial adsorption of Ag atoms on high-index Si(5 5 12), was investigated by scanning tunneling microscopy.•The Ag atoms preferentially adsorb on the site between the tetramer in D1 section and p chain.•The Ag atoms initially adsorb on a special site keeping the periodicity of substrateAdsorption of Ag atoms on Si(7 7 17) existing on Si(5 5 12) under compressive stress induces double Ag rows.•Ag nanostructure formed on Si(5 5 12) shows the metallic feature.