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It is known that alkali-metal graphite intercalation compounds (AGIC) have catalytic activities for hydrogen layer of the compounds. The behaviors of these compounds have been known to depend on the structure, sort of metals and temperature. Hydrogens are physisorptively accommodated in the molecules in the interstices among the alkali-metal ions in intercalant layers of stage-2 compounds C24M (M=K, Rb and Cs) at temperatures below 200 K [1–3]. Chemisorption of hydrogen takes place in both first and second stage compounds at higher temperatures [4, 5]. In order to clarify the mechanism of hydrogen chemisorption in the graphite compounds and properties of hydrogen-absorbed graphite compounds, several studies have been carried out. The change in magnetic susceptibilities as a function of hydrogen content has been investigated for hydrogen-chemisorbed C8K [6]. It has been suggested that dissolved hydrogen in C8K is paramagnetic by means of magnetic resonance studies [7]. The studies of means of ESR and electrical conductivity [8] have shown that in C8K, C24K, and C24Rb, the hydride ions are stabilized after the dissociation of the hydrogen molecules into atoms and the subsequent charge transfer, and in C8Rb hydrogens are absorbed in the atomic form. Recently the present authors have discussed the mechanism of anomalous magnetic effect due to hydrogen uptake in C8RbHx with the theoretical formula, which is extended from “topological quasi-hydrogen” model [24]. It is suggested strongly that the hydrogen state in C8RbHx might have the Kondo-like property [24]. Positron annihilation spectroscopy is a useful method in the study of electronic structures of materials. This spectroscopy has been used in the investigation of electronic structures in graphite and AGICs. The momentum distribution of σand π-electrons in a graphite crystal have been studied by angular correlation of positron annihilation radiation (ACPAR) [9–12], and by Dopplerbroadening positron annihilation radiation (DBPAR) [13]. ACPAR spectra of C8K and C24K, after subtraction of a broad contributions which accounts for annihilation with the graphite σ and π-electrons. Features of the nar-

Positron Energy Loss and the Interaction between Positrons and Soliton-Like Electron Density in Graphite-Alkali Metal Intercalation Compounds