  We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn
quasicrystal overlayer on the 5-fold symmetric surface of an icosahedral
Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by
x-ray photoelectron diffraction, low-energy electron diffraction and electron
backscatter diffraction. This overlayer is also characterized by a reduced
density of states near the Fermi edge as expected for quasicrystals. This is
the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn
is obtained, studied and compared to its icosahedral counterpart.
