  Unsaturated magnetoresistance (MR) has been reported in WTe2, and remains
irrepressible up to very high field. Intense optimization of the crystalline
quality causes a squarely-increasing MR, as interpreted by perfect compensation
of opposite carriers. Herein we report our observation of linear MR (LMR) in
WTe2 crystals, the onset of which is first identified by constructing the
mobility spectra of the MR at low fields. The LMR further intensifies and
predominates at fields higher than 20 Tesla while the parabolic MR gradually
decays. The LMR remains unsaturated up to a high field of 60 Tesla and
persists, even at a high pressure of 6.2 GPa. Assisted by density functional
theory calculations and detailed mobility spectra, we find the LMR to be robust
against the applications of high field, broken carrier balance, and mobility
suppression. Angle-resolved photoemission spectroscopy reveals a unique
quasilinear energy dispersion near the Fermi level. Our results suggest that
the robust LMR is the low bound of the unsaturated MR in WTe2.
