  The extremely large magnetoresistance (XMR) in nonmagnetic semimetals has
inspired growing interest owing to both intriguing physics and potential
applications. We report results of synchrotron X-ray diffraction (SXRD) and
electrical transport measurements on TaAs2 under pressure up to ~ 37 GPa, which
revealed an anisotropic compression of the unit cell, formation of unusual
As-As bonds above 9.5 GPa, and enhancement of metallicity. Interestingly, the
MR of TaAs2 under pressure changed gently, which at 1.7 GPa is 96.6% and at
36.6 GPa is still 36.7%. The almost robust MR under pressure could be related
to the nearly stable electronic structure unveiled by the ab initio
calculations. The discovery would expand the potential use of XMR even under
high pressure.
