Exploring the tuning of Kondo insulators—strongly correlated electron systems in which the Kondo interaction of localized electrons (typically of unfilled f-shells of rare earth elements) with conduction electrons leads to the opening of a narrow energy gap at the Fermi level—we have recently discovered Weyl semimetal behavior in the cubic, noncentrosymmetric material Ce₃Bi₄Pd₃.This system exhibits exotic properties that set it well apart from weakly interacting Weyl semimetals:

• Specific heat reveals linearly dispersing electronic bands (the Weyl cones) with extremely low velocities, which evidences their strongly correlated nature.
• A giant spontaneous Hall effect, and an associated even-in-magnetic field Hall component; as the material preserves time reversal symmetry, this must be attributed to Berry curvature singularities at the Weyl nodes. The giant size of the effect reveals that the Weyl nodes are pinned to the close vicinity of the Fermi energy.
• Under magnetic field tuning, the Weyl nodes annihilate at a first (topological) quantum phase transition. At higher fields, the system metallizes, with signatures of quantum criticality in the high-field metallic phase.

Fig.1: The electronic specific heat coefficient is linear in the square of temperature, evidencing a linear electronic dispersion [from Dzsaber et al., Phys. Rev. Lett. 118, 246601 (2017)].

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