  Following on the success of the recent application of holographic LEED to the
determination of the 3D atomic geometry of Si adatoms on a SiC(111) p(3x3)
surface, which enabled that structure to be solved, we show in this paper that
a similar technique allows the direct recovery of the local geometry of
adsorbates forming superstructures as small as p(2x2), even in the presence of
a local substrate reconstruction.
