  We study possible Weyl semimetals of strongly-correlated electrons by
investigating magnetotransport properties in pyrochlore R2Ir2O7 (R=rare-earth
ions), choosing three types of R ions to design the exchange coupling scheme
between R 4f and Ir 5d moments; non-magnetic Eu (4f6), isotropic Gd (4f7), and
anisotropic Tb (4f8). In the doping-induced semimetallic state, distinctive
features of magnetoresistance and Hall effect are observed in R=Gd and Tb
compounds due to the effects of the exchange-enhanced isotropic and anisotropic
Zeeman fields, respectively, exemplifying the double Weyl semimetal and the
2-in 2-out line-node semimetal as predicted by theories. In particular, a Hall
angle of R=Gd compound is strongly enhanced to 1.5 % near above the critical
doping for the Mott transition. Furthermore, an unconventional Hall
contribution is discerned for a lower doping regime of R=Gd compound, which can
be ascribed to the emergence of Weyl points with the field-distorted all-in
all-out order state. These findings indicate that the hole-doping induced Mott
transition as well as the characteristic f-d exchange interaction stabilizes
versatile topological semimetal states in a wide range of material parameter
space.
