Table 1Experimental and calculated material parameters in Bi-III and in the reference materials In_{5}Bi_{3} and Ca_{3}Rh_{4}Sn_{13} (see text).

The coherence length ξ_{exp} is obtained from the upper critical field and can be compared to ξ_{calc} = ℏv_{F}/(πΔ). The Fermi velocity v_{F} is estimated by scaling the density functional theory (DFT) estimate by (1 + λ_{ρ})^{−1}, where λ_{ρ}, the electron-phonon coupling constant obtained from the slope of ρ(T) with the help of a DFT estimate of the plasma frequency Ω_{p} (see text), is listed separately. In In_{5}Bi_{3} and Ca_{3}Rh_{4}Sn_{13}, it can be compared to the ratio of measured and calculated Sommerfeld coefficients λ_{C} = γ_{exp}/γ_{DFT}−1. In Bi-III, no heat capacity data are as yet available. The gap size 2Δ = ηk_{B}T_{c} with η = 5.7 for Ca_{3}Rh_{4}Sn_{13} (27) and values ≃ 5 and 4 assumed for Bi-III and In_{5}Bi_{3} (Supplementary Materials). n/a, not applicable.