  We report fabrication of EuSb$_2$ single-crystalline films and investigation
of their quantum transport. First-principles calculations demonstrate that
EuSb$_2$ is a magnetic topological nodal-line semimetal protected by
nonsymmorphic symmetry. Observed Shubnikov-de Haas oscillations with multiple
frequency components exhibit small effective masses and two-dimensional
field-angle dependence even in a 250 nm thick film, further suggesting possible
contributions of surface states. This finding of the high-mobility magnetic
topological semimetal will trigger further investigation of exotic quantum
transport phenomena by controlling magnetic order in topological semimetal
films.
