  Detailed experimental and theoretical studies of the low-temperature specific
heat, magnetic susceptibility, thermal expansion and magnetostriction of the
orthorhombic compound CeNiSn are presented. All anomalies observed in the
thermodynamic and magnetic properties of CeNiSn are explained in a framework of
a model of metallic Kondo lattice with well developed spin-liquid-type
excitations. The pseudogap behavior of these excitations appears due to
interplay between spin-fermions and soft crystal-field (CF) states. The
thermodynamic relations for the spin liquid are derived. Together with the
explanation of inelastic neutron scattering spectra given earlier within a same
approach these studies of the low-temperature thermodynamics and magnetic
response give a consistent description of the nature of anomalies in the
low-temperature thermodynamics of perfect and imperfect CeNiSn crystals.
