  Angle-resolved spin-torque ferromagnetic resonance measurements are carried
out in heterostructures consisting of Py (Ni$_{81}$Fe$_{19}$) and a
noncollinear antiferromagnetic quantum material $\gamma-$IrMn$_{3}$. The
structural characterization reveals that $\gamma-$IrMn$_{3}$ is polycrystalline
in nature. A large exchange bias of 158~Oe is found in Py/$\gamma-$IrMn$_{3}$
at room temperature, while $\gamma-$IrMn$_{3}$/Py and Py/Cu/$\gamma-$IrMn$_{3}$
exhibited no exchange bias. Regardless of the exchange bias and stacking
sequence, we observe a substantial unconventional out-of-plane anti-damping
torque when $\gamma-$IrMn$_{3}$ is in direct contact with Py. The magnitude of
the out-of-plane spin-orbit torque efficiency is found to be twice as large as
the in-plane spin-orbit torque efficiency. The unconventional spin-orbit torque
vanishes when a Cu spacer is introduced between Py and $\gamma-$IrMn$_{3}$,
indicating that the unconventional spin-orbit torque in this system originates
at the interface. These findings are important for realizing efficient
antiferromagnet-based spintronic devices via interfacial engineering.
