High resolution experiment on the electronic density of states in icosahedral-Al-Pd-Mn

We present experiments of photoemission and tunneling spectroscopy which in dicate the presence of a dip in the density of states around the level E-F in the icosahedral-Al-Pd-Mn (i-Al-Pd-Mn) phase. From high resolution photoe mission experiments on a single grain of i-Al-Pd-Mn, we have got clear evid ence that the surface state (quasicrystalline or disordered) strongly affec ts the measured density of states. For a quasicrystalline surface we observ e a pseudo-gap feature at E-F. The remaining density of states at E-F is co mpatible with the gamma term of specific heat. The band edge shows a square root dependence in the vicinity of E-F. This is similar to the single squa re root anomaly found by tunneling spectroscopy around E-F in the range +/- 300 meV. The photoemission data show a filling of this feature for the diso rdered surface where a Fermi edge clearly develops. (C) 2000 Elsevier Scien ce B.V. Ail rights reserved.