  Transition metal dichalcogenides like 2H-NbSe2 in their two-dimensional (2D)
form exhibit Ising superconductivity with the quasiparticle spins are firmly
pinned in the direction perpendicular to the basal plane. This enables them to
withstand exceptionally high magnetic fields beyond the Pauli limit for
superconductivity. Using field-angle-resolved magnetoresistance experiments for
fields rotated in the basal plane we investigate the field-angle dependence of
the upper critical field (Hc2), which directly reflects the symmetry of the
superconducting order parameter. We observe a six-fold nodal symmetry
superposed on a two-fold symmetry. This agrees with theoretical predictions of
a nodal topological superconducting phase near Hc2, together with a nematic
superconducting state. We demonstrate that in NbSe2 such unconventional
superconducting states can arise from the presence of several competing
superconducting channels.
