  We report the topological electronic structure, magnetic, and
magnetotransport properties of a noncentrosymmetric compound GdAlSi. Magnetic
susceptibility shows an antiferromagnetic transition at $T_\mathrm{N}$ = 32 K.
In-plane isothermal magnetization exhibits an unusual hysteresis behavior at
higher magnetic field, rather than near zero field. Moreover, the hysteresis
behavior is asymmetric under positive and negative magnetic fields.
First-principles calculations were performed on various magnetic
configurations, revealing that the antiferromagnetic state is the ground state,
and the spiral antiferromagnetic state is a close competing state. The
calculations also reveal that GdAlSi hosts multiple Weyl points near the Fermi
energy. The band structure measured by angle-resolved photoemission
spectroscopy (ARPES) shows relatively good agreement with the theory, with the
possibility of Weyl nodes slightly above the Fermi energy. Within the magnetic
ordered state, we observe an exceptionally large anomalous Hall conductivity
(AHC) of ~ 1310 $\Omega^{-1}$cm$^{-1}$ at 2 K. Interestingly, the anomalous
Hall effect persists up to room temperature with a significant value of AHC (~
155 $\Omega^{-1}$cm$^{-1}$). Our analysis indicates that the large AHC
originates from the Berry curvature associated with the multiple pairs of Weyl
points near Fermi energy.
