Low-temperature properties of La1-xCaxMnO3 single crystals:: comparison with La1-xSrxMnO3

We have investigated, in single crystals of La1-xCaxMnO3, the insulator-metal (IM) transition at the ground state induced by carrier doping or applying pressure around the critical doping level (x(c)approximate to 0.22). The up turn of the resistivity in the IM critical region has been found under a pressure below the Curie temperature (Tc) perhaps due to the proximity to the orbital-ordered ferromagnetic insulating phase. Around the IM transition the additional T-3 and T-1.5 components are clearly observed in the specific heat, while the T-2 coefficient of the resistivity and the residual resistivity is much enhanced in the metallic region in the vicinity of the transition. These results reveal the subsistence of the charge/orbital correlation in the metallic ground state.