Fermi surface of the Pr-based filled skutterudite compound PrOs4P12

We have investigated the Fermi-surface (FS) properties in the Pr-based filled skutterudite ${\text{PrOs}}_{4}{\text{P}}_{12}$ and its reference compound ${\text{LaOs}}_{4}{\text{P}}_{12}$ by means of de Haas--van Alphen experiments and the band-structure calculations. The topology of FS in ${\text{PrOs}}_{4}{\text{P}}_{12}$ is close to that in the reference compound ${\text{LaOs}}_{4}{\text{P}}_{12}$, indicating a localized nature of $4f$ electrons in ${\text{PrOs}}_{4}{\text{P}}_{12}$. Whereas the localized nature of $4f$ electrons, we have confirmed a highly enhanced cyclotron effective mass of up to $18{m}_{0}$ in ${\text{PrOs}}_{4}{\text{P}}_{12}$, which is enhanced about 3.8 times compared to that in ${\text{LaOs}}_{4}{\text{P}}_{12}$. No nesting property with $q=(1,0,0)$ in the FS of ${\text{PrOs}}_{4}{\text{P}}_{12}$ has been confirmed in contrast to good nesting properties in ${\text{PrFe}}_{4}{\text{P}}_{12}$ and ${\text{PrRu}}_{4}{\text{P}}_{12}$ which exhibit unusual ordered states at low temperatures. A role of both the $4f$ electron's contributions and the FS nesting property for unusual phase transitions are discussed.