  The anomalous Hall effect (AHE), a Hall signal occurring without an external
magnetic field, is one of the most significant phenomena. However,
understanding the AHE mechanism has been challenging and largely restricted to
ferromagnetic metals. Here, we investigate the recently discovered AHE in the
chiral antiferromagnet Mn3Sn by measuring a thermal analog of the AHE, known as
an anomalous thermal Hall effect (ATHE). The amplitude of the ATHE scales with
the anomalous Hall conductivity of Mn3Sn over a wide temperature range,
demonstrating that the AHE of Mn3Sn arises from a dissipationless intrinsic
mechanism associated with the Berry curvature. Moreover, we find that the
dissipationless AHE is significantly stabilized by shifting the Fermi level
toward the magnetic Weyl points. Thus, in Mn3Sn, the Berry curvature emerging
from the proposed magnetic Weyl fermion state is a key factor for the observed
AHE and ATHE.
