  The anomalous Hall effect (AHE) is a quantum coherent transport phenomenon
that conventionally vanishes at elevated temperatures because of thermal
dephasing. Therefore, it is puzzling that the AHE can survive in heavy metal
(HM)/antiferromagnetic (AFM) insulator (AFMI) heterostructures at high
temperatures yet disappears at low temperatures. In this paper, we report that
an unconventional high-temperature AHE in HM/AFMI is observed only around the
N\'eel temperature of AFM, with large anomalous Hall resistivity up to 40
n$\Omega$ cm. This mechanism is attributed to the emergence of a noncollinear
AFM spin texture with a non-zero net topological charge. Atomistic spin
dynamics simulation shows that such a unique spin texture can be stabilized by
the subtle interplay among the collinear AFM exchange coupling, interfacial
Dyzaloshinski-Moriya interaction, thermal fluctuation, and bias magnetic field.
