Symmetrized Fermi surface of the Tl-adsorbed Au/Si(111)√3×√3 surface determined with ARPES. The k-space area where the ARPES measurements were carried out is outlined by a dashed blue line. (b) Constant energy contours. Arrows along the contours and their length indicate the in-plane spin component. The out-of-plane spin component is indicated by the colour with red and blue corresponding to the upward and downward directions, respectively. White colour indicates fully in-plane spin alignment. (c) Azimuthal dependence of the Fermi wave vector kF for the S1A and S2B bands. Experimental and calculated data are presented by dots and solid lines, respectively. (d) Azimuthal dependencies of the spin components, including in-plane components in the directions tangential and normal to the Fermi contour (upper panel) and out-of-plane component (lower panel).