  We use high resolution angle-resolved photoemission spectroscopy (ARPES) and
electronic structure calculations to study the electronic properties of
rare-earth monoantimonides RSb (R = Y, Ce, Gd, Dy, Ho, Tm, Lu). The
experimentally measured Fermi surface (FS) of RSb consists of at least two
concentric hole pockets at the $\Gamma$ point and two intersecting electron
pockets at the $X$ point. These data agree relatively well with the electronic
structure calculations. Detailed photon energy dependence measurements using
both synchrotron and laser ARPES systems indicate that there is at least one
Fermi surface sheet with strong three-dimensionality centered at the $\Gamma$
point. Due to the "lanthanide contraction", the unit cell of different
rare-earth monoantimonides shrinks when changing rare-earth ion from CeSb to
LuSb. This results in the differences in the chemical potentials in these
compounds, which is demonstrated by both ARPES measurements and electronic
structure calculations. Interestingly, in CeSb, the intersecting electron
pockets at the $X$ point seem to be touching the valence bands, forming a
four-fold degenerate Dirac-like feature. On the other hand, the remaining
rare-earth monoantimonides show significant gaps between the upper and lower
bands at the $X$ point. Furthermore, similar to the previously reported results
of LaBi, a Dirac-like structure was observed at the $\Gamma$ point in YSb,
CeSb, and GdSb, compounds showing relatively high magnetoresistance. This
Dirac-like structure may contribute to the unusually large magnetoresistance in
these compounds.
