Intercalation provides an effective approach to reducing the dimensionality and modifying the electronic structure of layered materials. Here, we report the intercalation of organic molecules into the van der Waals materials ${\mathrm{HfTiTe}}_4$ and ${\mathrm{TaRhTe}}_4$, which are theoretically predicted to be two-dimensional topological insulators in their monolayer forms. In ${\mathrm{HfTiTe}}_4$, intercalation resulted in an overall increase of resistivity, while preserving the metallic temperature dependence of the pristine compound. The magnetoresistance exhibited a weak antilocalization behavior, indicative of reduced dimensionality. Band structure calculations revealed that the band topology of intercalated ${\mathrm{HfTiTe}}_4$ corresponds to that of a weak topological insulator, although there is a band that crosses the Fermi level, which explains the observed metallic behavior. For ${\mathrm{TaRhTe}}_4$, on the other hand, the temperature dependence of resistivity changed from metallic to insulating by the intercalation. Moreover, magnetotransport measurements provided evidence of topological edge states, supporting the prediction that monolayer ${\mathrm{TaRhTe}}_4$ is a two-dimensional topological insulator. The band calculations indicated that the intercalation caused a bulk gap opening at the Fermi level and the electronic structure is very similar to that of a monolayer ${\mathrm{TaRhTe}}_4$, in agreement with the transport properties.

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• Intercalation
• Layered crystals
• Topological materials
• Two-dimensional electron system
• Density functional calculations