Quantum Oscillations in the Specific Heat of Kondo Insulator YbB₁₂

We observe the magnetic quantum oscillation in specific heat of the Kondo insulator YbB₁₂.

The frequency of these oscillations F = 670 T, aligns with findings from magnetoresistance and

torque magnetometry experiments for μ₀H > 35 T in the Kondo insulating phase. Remarkably, the

quantum oscillation amplitudes in the specific heat are substantial, with ∆C/T ≈ 0.5 mJ mol⁻¹K⁻²

at 0.5 K, accounting for 13% of the known linear heat capacity coefficient γ. Double-peak structures

of quantum oscillations based on the distribution function of fermions were identified and used to

determine the value of the effective mass in the specific heat, which agrees well with the torque

magnetometry. These observations support charge-neutral fermions contributing to the quantum

oscillations in YbB12.