NEAR-ORDER STRUCTURE AND SYMMETRY ELEMENTS OF AN ICOSAHEDRAL QUASI-CRYSTAL ALLOY - AL70MN9PD21

The presence of twofold-, threefold- and fivefold-symmetry elements in an icosahedral quasicrystal, Al70Mn9Pd21, can be deduced from observa tions in real space, using the technique of secondary-electron imaging . The angles measured between different symmetry axes confirm the icos ahedral point-group symmetry (($) over bar 5 ($) over bar 3m) in the i nvestigated alloy. The clusters having this local point symmetry must have identical orientation and most probably occur in large amounts in the quasicrystal material.