TRANSPORT STUDY OF (T,P) PHASE-DIAGRAM IN PDAL2CL8 INTERCALATED GRAPHITE

We have examined the c-direction variations of resistance, R(c) (or re sistivity, rho(c)) over the 4.2-295 K temperature range at ambient pre ssure, and over the 160-295 K range for pressures up to 1.5 GPa on fir st stage PdAl2Cl8 graphite intercalation compounds. All samples examin ed manifest a rapid, nonlinear decrease in R(c) with pressure (maximum \d ln R(c)/dp\ > 300% GPa(-1) at 0.4 GPa. The overall R(c) decrease i s around 90% by 1 GPa, a value greater than that observed in any other GIC to date. Upon slow pressure release, the resistance increases lin early but to only about 20-25% of its initial (1 bar) value for HOPG-b ased materials: on the contrary, it returns along its initial R-p traj ectory for GICs based on single crystal graphite. We discuss these dat a with reference to the X-ray diffraction results, to the significance of the residual resistivity and to studies on other similar lamellar solids.