  We present the results of a crystal structure determination using neutron
powder diffraction as well as the superconducting properties of the rare-earth
sesquicarbide La2C3 (Tc ~ 13.4 K) by means of specific heat and upper critical
field measurements. From the detailed analysis of the specific heat and a
comparison with ab-initio electronic structure calculations, a quantitative
estimate of the electron-phonon coupling strength and the logarithmic average
phonon frequency is made. The electron-phonon coupling constant is determined
to \lambda ~ 1.35. The electron-phonon coupling to low energy phonon modes is
found to be the leading mechanism for the superconductivity. Our results
suggest that La2C3 is in the strong coupling regime, and the relevant phonon
modes are La-related rather than C-C stretching modes. The upper critical field
shows a clear enhancement with respect to the Werthamer-Helfand-Hohenberg
prediction, consistent with strong electron-phonon coupling. Possible effects
on the superconducting properties due to the noncentrosymmetry of the crystal
structure are discussed.
