  The superconducting energy gap and quasiparticle density of states (DOS) is
measured by means of Andreev-reflection spectroscopy in normal metal -
superconductor point contacts. It is found that both in paramagnetic and in
antiferromagnetically ordered states (Tm- and Dy-compounds) the DOS has the
BCS-like form while in Er- the dip in the temperature dependence of the gap is
observed at the Neel temperature. In Ho-compound, the non-BCS-like form of DOS
is observed in the temperature region where the incommensurate spin density
waves exist along the axes a and c .
  Inelastic point-contact spectroscopy performed on these compounds shows that
the low-frequency phonons are important for the superconducting state which are
strongly mixed with the magnetic excitation branches in magnetic
superconductors.
