  Realizing ideal Weyl semimetal state with a single pair of Weyl points has
been a long-sought goal in the field of topological semimetals. Here, we reveal
such a state in the Cr-based half-Heusler compounds XCrTe (X=K, Rb). We show
that these materials have a half metal ground state, with Fermi level crossing
only one spin channel. Importantly, the Fermi surface is clean, consisting of
the minimal number (i.e., a single pair) of spin-polarized Weyl points, so the
state represents an ideal Weyl half semimetal. We show that the locations of
the two Weyl points and the associated Chern vector can be flexibly tuned by
rotating the magnetization vector. The minimal surface Fermi arc pattern and
its contribution to anomalous Hall transport are discussed. Our finding offers
an ideal material platform for exploring magnetic Weyl fermions, which will
also facilitate the interplay between Weyl physics and spintronics.
