  It is well known that the (1x5) superstructure of Bi cuprate superconductors
will be suppressed due to optimum doping with Pb. Nevertheless, a Fermi surface
map of (Pb,La)-Bi2201 (Pb = 0.4 and La = 0.4) determined by angular resolved
photoemission (ARPES) revealed additional Fermi surface features. Low energy
electron diffraction and X-ray diffraction of these samples showed no sign of
any superstructure. Scanning tunneling microscopy (STM), on the other hand,
revealed two distinct modulations of the charge density, one of (1x32) and a
second of (6x6) periodicity. The wave vectors of both modulations have been
extracted and used to simulate the corresponding Fermi surface, which is
compared with the experimental one. The origin of these modulations is
discussed in terms of dopant ordering.
