  We report on the highly efficient spin-orbit torque (SOT) generation in
epitaxial SrIrO$_{3}$(SIO), which is grown on an orthorhombic DyScO$_{3}$(110)
substrate. By conducting harmonic Hall measurement in
Co$_{20}$Fe$_{60}$B$_{20}$ (CoFeB)/SIO bilayers, we characterize two kinds of
the SOTs, i.e., dampinglike (DL) and fieldlike ones to find that the former is
much larger than the latter. By comparison with the Pt control sample with the
same CoFeB thickness, the observed DL SOT efficiency $\xi$$_{DL}$ of SIO
($\sim$0.32) is three times higher than that of Pt ($\sim$0.093). The
$\xi$$_{DL}$ is nearly constant as a function of the CoFeB thickness,
suggesting that the SIO plays a crucial role in the large SOT generation. These
results on the CoFeB/SIO bilayers highlight that the epitaxial SIO is promising
for low-current and reliable spin-orbit torque-controlled devices.
