We report thermal expansion measurements on Ca(Fe_(1-x)Co_x)_2As_2 single
crystals with different thermal treatment, with samples chosen to represent
four different ground states observed in this family. For all samples thermal
expansion is anisotropic with different signs of the in-plane and c-axis
thermal expansion coefficients in the high temperature, tetragonal phase. The
features in thermal expansion associated with the phase transitions are of
opposite signs as well, pointing to a different response of transition
temperatures to the in-plane and the c-axis stress. These features, and
consequently the inferred pressure derivatives, are very large, clearly and
substantially exceeding those in the Ba(Fe_(1-x)Co_x)_2As_2 family. For all
transitions the c-axis response is dominant
