Point-contact investigations of challenging superconductors: two-band MgB2, antiferromagnetic HoNi2B2C, heavy-fermion UPd2Al3, paramagnetic MgCNi3

Abstract An overview on recent efforts in point-contact (PC) spectroscopy of title superconductors is given. Distinct phonon features and crystalline-electric field effects are observed in PC spectra of HoNi2B2C. Results of study of superconducting (SC) gap and excess current versus temperature and magnetic field reflecting specific multi-band electronic structure in MgB2 are presented. The nature of the extremely nonlinear I ( V ) curves in the antiferromagnetic (AF) and SC state are elucidated for UPd2Al3 break junctions and MgCNi3 point contacts.