  Magnetic Weyl semimetal (MWS) is a unique topological state with open surface
Fermi arc states and other exotic transport phenomena. However, most reported
MWSs show multiple pairs of Weyl points and complicated Fermi surfaces, which
increases the difficulty of the investigation into the intrinsic chiral
transport property. In this wor, we successfully synthesized a soft magnetic
Weyl semimetal Eu$_3$In$_2$As$_4$ with a single pair of Weyl points under
magnetic fields. The Shubnikov de Haas (SdH) oscillation with a single
frequency, as well as a linear hall resistance with the same carrier density,
is observed up to 50 Tesla, indicating a single pair of Weyl points around the
Fermi level with a massless fermion ($m^* = 0.121 m_0$, $\pi$ Berry phase).
Such a single pair of Weyl points is further confirmed by the density
functional theory calculations. The magnetic ordering and band topology can be
easily tuned by the external magnetic field. The field-induced MWS
Eu$_3$In$_2$As$_4$ with a single pair of Weyl points is a good platform to
detect chiral transport properties, including possible quantum anomalous Hall
effect.
