  The semimetal antimony (Sb) element doped into hydrogen has been performed
theoretically to explored high-pressure crystal structure and superconductivity
of antimony hydrides. The unexpected stoichiometry $\textrm{SbH}_\textrm{4}$
with $P6_3/mmc$ symmetry is found to have most negative enthalpy and embody the
coexistence of covalent and ionic bonds. It is a metallic phase and stable in
the pressure ranges of 127-300 GPa. Furthermore, a superconducting critical
temperature ($T_c$) of 106 K is obtained at 150 GPa by employing the
Allen-Dynes modified McMillan equation. In addition, an extrusive
distinguishing feature is the presence of soft phonon modes, which is primary
contribution to the strength of electron-phonon coupling.
