Stage-1 potassium-mercury–graphite intercalation compounds with markedly different superconducting transition temperatures $T_c$ and transition widths Δ$T_c$ are found to have uniformly high $T_c$ and narrow transitions after exposure to hydrogen. These hydrogen-doping experiments suggest a schematic model for the density of states in stage-1 potassium-mercury–graphite intercalation compounds.

• Received 11 April 1985

DOI:https://doi.org/10.1103/PhysRevB.32.533