For and 4 under hydrostatic pressure

The hydrostatic pressure effects on the superconducting transition temperatures (Formula presented) of the oxycarbonate cuprates (Formula presented) have been determined for (Formula presented) and 4 with different dopings of (Formula presented)’s. We found that, similar to (Formula presented) depends strongly on x for (Cu, C)-1223 and increases from (Formula presented) to (Formula presented) as x decreases and the compound changes from overdoped to nearly optimally doped, consistent with the prediction of the phenomenological model on the pressure effect on (Formula presented) In contrast to the prediction, (Formula presented) depends only slightly on x for (Cu, C)-1234 and decreases from (Formula presented) to (Formula presented) as x decreases from nearly optimally doped to underdoped. The (Formula presented) difference is attributed to the possible different electronic contribution of the CuO chains in the two compounds, as implied by the distinct temperature dependences of their thermoelectric power.