LEED study of the orthorhombic Al$_{13}$Co$_{4}$ (100) surface and its interaction with Xe

The (100) surface of orthorhombic Al$_{13}$Co$_{4}$ is a periodic approximant of the decagonal Al-Ni-Co 10-fold quasicrystalline surface. An STM study [1] of Al$_{13}$Co$_{4 }$ shows the surface has two different terminations and that the relative amounts of each are dependent on the surface preparation. We will present a dynamical LEED study of the T1-termination of the Al$_{13}$Co$_{4}$(100) surface, obtained by annealing at 1173K for 2 hours. Xe adsorbs on this surface in a layer-by-layer growth mode, and at a sufficiently high coverage it orders into four domains of close-packed Xe. These domains are rotationally aligned along certain crystallographic directions, where they appear to lock into uniaxial higher-order commensurate structures. The structures and thermodynamics of Xe film growth will be presented.\\[4pt] [1] R. Addou et.al, Physical Review B 80, 014230(2009).