We present the results of the first experimental study of ionization yield of electron recoils with energies below 100 keV produced in liquid xenon by the isotopes: 37 Ar, 83m Kr, 241 Am, 129 Xe, 131 Xe. It is confirmed by a direct measurement with 37 Ar isotope (2.82 keV) that the ionization yield is growing up with the energy decrease in the energy range below ~ 10 keV accordingly to the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be 25 ± 3 ns at the electric field of 3.75 kV/cm.