  Temperature evolution of the 2H-TaSe2 Fermi surface (FS) is studied by
high-resolution angle-resolved photoemission spectroscopy (ARPES).
High-accuracy determination of the FS geometry was possible after measuring
electron momenta and velocities along all high-symmetry directions as a
function of temperature with subsequent fitting to a tight-binding model. The
estimated incommensurability parameter of the nesting vector agrees with that
of the incommensurate charge modulations. We observe detectable nonmonotonic
temperature dependence of the FS shape, which we show to be consistent with the
analogous behavior of the pseudogap. These changes in the electronic structure
could stem from the competition of commensurate and incommensurate charge
density wave order fluctuations, explaining the puzzling reopening of the
pseudogap observed in the normal state of both transition metal dichalcogenides
and high-Tc cuprates.
