  In band theory of solids, degeneracies manifest themselves as point, line,
and surface objects. The topological nature of band degeneracies has recently
been appreciated since the recognition of gapless topological quantum phases of
matter. Based on first-principles calculations, we report the topological
semimetal phase in osmium oxyhalide OsOF$_5$ that exhibits zero-dimensional
Weyl points, one-dimensional nodal lines, and two-dimensional nodal surfaces.
The semimetal phase is ensured by the electron filling constraint while band
degeneracies of various dimensionalities are protected by the nonsymmorphic
crystalline symmetries. Focusing on two nodal loops crossing the Fermi level,
we demonstrate their topological protection by $\pi$ Berry phase and describe
the drumhead surface states topologically connected by nontrivial
$\mathbb{Z}_2$ index. Our prediction highlights OsOF$_5$ as a unique
topological material in which a rich variety of topological degeneracies exists
in a narrow energy range close to the Fermi level owing to the molecular
crystal structure of this material.
