Point-contact study of the LuNi2B2C borocarbide superconducting film

We present point-contact (PC) Andreev-reflection measurements of a superconducting epitaxial c-axis oriented nickel borocarbide film LuNi2B2C (T-c = 15.9 K). The averaged value of the superconducting gap is found to be Delta similar or equal to 2.6 +/- 0.2 meV in the one-gap approach, whereas the two-gap approach results in Delta(1) similar or equal to 2.14 +/- 0.36 meV and Delta(2) similar or equal to 3 +/- 0.27 meV. The better fit of the Andreev-reflection spectra for the LuNi2B2C-Cu PC obtained by the two-gap approach provides evidence for multiband superconductivity in LuNi2B2C. For the first time, PC electron-phonon interaction (EPI) spectra have been measured for this compound. They demonstrate a pronounced phonon maximum at 8.5 +/- 0.4 meV and a second shallow one at 15.8 +/- 0.6 meV. The electron-phonon coupling constant lambda estimated from the PC EPI spectra turned out to be small (with lambda(PC) similar to 0.1), like in other superconducting rare-earth nickel borocarbides. Possible reasons for this are discussed.