Pressure dependence of the superconducting transition temperature of the stage-2 potassium mercurographitide intercalation compound

Measurements of the pressure (P) dependence of the superconducting transition temperature T_c of stage-two KHgC₈ are reported. T_c is found to decrease with applied pressure from a room pressure value of 1.85K at a rate dT_c/dP=-6.5 × 10^-5K/bar, similar to typical superconducting elements such as Sn. No superconductivity was detected for stage-one KHgC₄ or K_0.5Hg_0.5 amalgam to a limiting temperature T = 1.3K and a limiting pressure P = 22 kbar. These results are discussed in reference to the possible occurence of structural and charge density wave transitions in these materials and recent theoretical models of superconducting graphire intercalation compounds.