Superconductivity in TlBi$_2$ with a large Kadowaki-Woods ratio

In this article, the superconducting and normal state properties of TlBi$_2$ with the AlB$_2$-type structure were studied by the resistivity, magnetization and specific heat measurements. It was found that bulk superconductivity with $T_{C}$ = 6.2 K emerges in TlBi$_2$, which is a phonon-mediated $s$-wave superconductor with a strong electron-phonon coupling ($λ$$_{ep}$ = 1.38) and a large superconducting gap ($Δ_{0}$/$k_{B}T_{C}$ = 2.25). We found that the $ρ$($T$) exhibits an unusual $T$-linear dependence above 50 K, and can be well described by the Fermi-liquid theory below 20 K. Interestingly, its Kadowaki-Woods ratio $A/γ^{2}$ [9.2$\times$10$^{-5}$ $μΩ$ cm(mol K$^{2}$/mJ)$^{2}$] is unexpectedly one order of magnitude larger than that obtained in many heavy Fermi compounds, although the electron correlation is not so strong.