  The electronic band structure and Fermi surface of ZrTe_3 was precisely
determined by linearly polarized angle-resolved photoelectron spectroscopy.
Several bands and a large part of the Fermi surface are found to be split by
100-200 meV into two parallel dispersions. Band structure calculations reveal
that the splitting is due to a change of crystal structure near the surface.
The agreement between calculation and experiment is enhanced by including the
spin-orbit potential in the calculations, but the spin-orbit energy does not
lead to a splitting of the bands. The dispersion of the highly nested small
electron pocket that gives rise to the charge density wave is traceable even in
the low-temperature gapped state, thus implying that the finite correlation
length of the long-wavelength modulation leads to a smearing of the band
back-folding.
