  We performed calculations of the electronic band structure and the Fermi
surface as well as measured the longitudinal resistivity rhoxx(T,H), Hall
resistivity rhoxy(T,H) and quantum oscillations of the magnetization as a
function of temperature at various magnetic fields for MoO2 with monoclinic
crystal structure. The band structure calculations show that MoO2 is a
nodal-line semimetal when spin-orbit coupling is ignored. It was found that a
large magnetoresistance reaching 5.03x10^4% at 2 K and 9 T, its nearly
quadratic field dependence and a field-induced up-turn behavior of rhoxx(T),
the characteristics common for many topologically non-trivial as well as
trivial semimetals, emerge also in MoO2. The observed properties are attributed
to a perfect charge-carrier compensation, evidenced by both calculations
relying on the Fermi surface topology and the Hall resistivity measurements.
Both the observation of negative magnetoresistance for magnetic field along the
current direction and the non-zero Berry phase in de Haas-van Alphen
measurements indicate that pairs of Weyl points appear in MoO2, which may be
due to the crystal symmetry breaking. These results highlight MoO2 as a new
platform materials for studying the topological properties of oxides.
