  High-pressure electrical resistivity measurements reveal that the mechanical
deformation of ultra-hard WB2 during compression induces superconductivity
above 50 GPa with a maximum superconducting critical temperature, Tc of 17 K at
90 GPa. Upon further compression up to 190 GPa, the Tc gradually decreases.
Theoretical calculations show that electron-phonon mediated superconductivity
originates from the formation of metastable stacking faults and twin boundaries
that exhibit a local structure resembling MgB2} (hP3, space group 191,
prototype AlB2). Synchrotron x-ray diffraction measurements up to 145 GPa} show
that the ambient pressure hP12 structure (space group 194, prototype WB2)
continues to persist to this pressure, consistent with the formation of the
planar defects above 50 GPa. The abrupt appearance of superconductivity under
pressure does not coincide with a structural transition but instead with the
formation and percolation of mechanically-induced stacking faults and twin
boundaries. The results identify an alternate route for designing
superconducting materials.
