  We report experimental signatures of topological transitions among the Weyl
semimetal states of pyrochlore Pr2Ir2O7, where the Kondo coupling between the
Ir topological electrons and the spin-ice like orders of Pr moments plays a
decisive role. The magnetic-field dependence of resistivity and the Hall
conductivity exhibits a plateau and a sharp jump associated with a
magnetic-field hysteresis, similar to a liquid-gas-like transition in dipolar
spin ice system. Furthermore, the Kondo coupling is controlled by the
hydrostatic pressure, revealing that the field-induced displacement of Weyl
points in the momentum space strongly depends on the respective electronic
state as well as on the Kondo coupling strength. These observations pave a
route toward the engineering of band topology in hybrid quantum materials with
relativistic conduction electrons and localized magnetic moments.
