Anomalous low-temperature specific heat of charge-orderedLa0.5Ca0.5MnO3

We report a study of the specific heat, resistivity, and magnetization of ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_x$ for $x=0.47,$ 0.5, 0.53 with and without an applied magnetic field. In zero (earth) field we find that the charge-ordered materials $\mathrm{}(x=0.5,0.53\mathrm{})\mathrm{}$ have extra entropy of nonmagnetic origin at low temperature when compared to metallic and ferromagnetic compositions $\mathrm{}(x=0.47,0.2\mathrm{}).$ For the $x=0.5\mathrm{}$ compound the specific heat does not change in a 8.5 T field even though the resistivity decreases ten orders of magnitude.