  We have studied the nature of the surface charge distribution in CeTe3. This
is a simple, cleavable, layered material with a robust one-dimensional
incommensurate charge density wave (CDW). Scanning tunneling microscopy (STM)
has been applied on the exposed surface of a cleaved single crystal. At 77 K,
the STM images show both the atomic lattice of surface Te atoms arranged in a
square net and the CDW modulations oriented at 45 degrees with respect to the
Te net. Fourier transform of the STM data shows Te square lattice peaks, and
peaks related to the CDW oriented at 45 degrees to the lattice peaks. In
addition, clear peaks are present, consistent with subsurface structure and
wave vector mixing effects. These data are supported by electronic structure
calculations, which show that the subsurface signal most likely arises from a
lattice of Ce atoms situated 2.53 angstroms below the surface Te net.
