Heavy fermion superconductors often display upper critical fields that exceed the conventional Pauli paramagnetic limit, indicating that strong correlations and hybridized quasiparticle bands play an essential role in the paramagnetic pair-breaking process. Within the two-dimensional Kondo-Heisenberg model, we perform a self-consistent mean-field analysis of spin-singlet $s$-, extended-$s$-, and $d$-wave pairing under Zeeman fields and compute the critical field $B_c$, transition temperature $T_c$, and Clogston-Chandrasekhar ratio $r_{\mathrm{CC}}$. We find that $r_{\mathrm{CC}}$ increases sharply as the conduction filling approaches half filling. This enhancement arises from the weakly dispersive region of the lower hybridized band, where the strongly reduced Fermi velocity diminishes the normal-state paramagnetic energy and stabilizes superconductivity. At fixed filling, the distinct $J_H$ dependences among the three pairing channels reflect the sensitivity of Pauli limiting to both band curvature and the structure of the order parameter. These results provide microscopic evidence that proximity to a near-flat hybridized band offers a robust route to enhanced Pauli-limiting fields in heavy fermion superconductors.

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• Electronic structure
• Flat bands
• Heavy-fermion systems
• Strongly correlated systems
• Superconductors
• Kondo lattice model