  We observe unidirectional charge density wave ordering on the cleaved surface
of TbTe3 with a Scanning Tunneling Microscope at ~6 K. The modulation
wave-vector q_{CDW} as determined by Fourier analysis is 0.71 +/- 0.02 * 2
pi/c. (Where c is one edge of the in-plane 3D unit cell.) Images at different
tip-sample voltages show the unit cell doubling effects of dimerization and the
layer below. Our results agree with bulk X-ray measurements, with the addition
of ~(1/3) * 2 pi/a ordering perpendicular to the CDW. Our analysis indicates
that the CDW is incommensurate.
