  X-ray scattering by multiferroic LuFe2O4 is reported. Below 320 K,
superstructure reflections indicate an incommensurate charge order with
propagation close to (1/3,1/3,3/2). The corresponding charge configuration,
also found by electronic structure calculations as most stable, contains polar
Fe/O double-layers with antiferroelectric stacking. Diffuse scattering at 360
K, with (1/3,1/3,0) propagation, indicates ferroelectric short-range
correlations between neighboring double-layers. The temperature dependence of
the incommensuration indicates that charge order and magnetism are coupled.
