  We report the first observation of a pressure-induced breakdown of the 3D-DSM
state in Cd3As2, evidenced by a series of in-situ high-pressure synchrotron
X-ray diffraction (XRD) and single crystal transport measurements. We find that
Cd3As2 undergoes a structural phase transition from a metallic tetragonal (T)
phase in space group I41/acd to a semiconducting monoclinic (M) phase in space
group P21/c at critical pressure 2.57 GPa, above this pressure, an activation
energy gap appears, accompanied by distinct switches in Hall resistivity slope
and electron mobility. These changes of crystal symmetry and corresponding
transport properties manifest the breakdown of the 3D-DSM state in pressurized
Cd3As2.
