Fermi surface and mass enhancement in KFe${}_2$As${}_2$ from de Haas-van Alphen effect measurements

We report on a band structure calculation and de Haas-van Alphen measurements of KFe${}_2$As${}_2$. Three cylindrical Fermi surfaces are found. Effective masses of electrons range from 6 to 18$m_e$, $m_e$ being the free electron mass. Remarkable discrepancies between the calculated and observed Fermi surface areas and the large mass enhancement ($\gtrsim 3$) highlight the importance of electronic correlations in determining the electronic structures of iron pnicitide superconductors.