  Motivated by recent experimental progress in studying weak decays of the
$\Lambda_c$ baryon we investigate its semileptonic decays in the framework of
the relativistic quark model based on the quasipotential approach with the
QCD-motivated potential. The form factors of the $\Lambda_c\to \Lambda l\nu_l$
and $\Lambda_c\to nl\nu_l$ decays are calculated in the whole accessible
kinematical region without extrapolations and additional model assumptions.
Relativistic effects are systematically taken into account including
transformations of baryon wave functions from the rest to moving reference
frame and contributions of the intermediate negative-energy states. Baryon wave
functions found in the previous mass spectrum calculations are used for the
numerical evaluation. Comprehensive predictions for decay rates, asymmetries
and polarization parameters are given. They agree well with available
experimental data.
