  The recent discoveries of strikingly large zero-field Hall and Nernst effects
in antiferromagnets Mn$_3$$X$, ($X$ = Sn, Ge) have brought the study of
magnetic topological states to the forefront of condensed matter research and
technological innovation. These effects are considered fingerprints of Weyl
nodes residing near the Fermi energy, promoting Mn$_3$$X$, ($X$ = Sn, Ge) as a
fascinating platform to explore the elusive magnetic Weyl fermions. In this
review, we provide recent updates on the insights drawn from experimental and
theoretical studies of Mn$_3$$X$, ($X$ = Sn, Ge) by combining previous reports
with our new, comprehensive set of transport measurements of high-quality
Mn$_3$Sn and Mn$_3$Ge single crystals. In particular, we report
magnetotransport signatures specific to chiral anomalies in Mn$_3$Ge and planar
Hall effect in Mn$_3$Sn, which have not yet been found in earlier studies. The
results summarized here indicate the essential role of magnetic Weyl fermions
in producing the large transverse responses in the absence of magnetization.
