De Haas-Van Alphen Experiments on BaNi$_2$P$_2$

We have observed de Haas-van Alphen (dHvA) oscillations in BaNi$_2$P$_2$, which is isostructural with BaFe$_2$As$_2$ and becomes superconducting below $T_c$ ~ 3 K without doping [T. Mine et al., Solid State Commun. 147, 111 (2008)]. It is a suitable compound to study how differnet electronic structures are between iron and nickel-based superconductors. The single crystals used in the study were obtained by high- pressure synthesis. dHvA frequencies up to 8 kT were observed, and their sizes and angular dependences can be explained very well by a band-structure calculation. Effective masses are two to three times largere than the corresponding band masses, suggesting moderate mass enhancement due to electron-phonon and electron-electron interactions.