Anomalous Beating Pattern in Wurtzite Al$_{x}$Ga$_{1-x}$N/GaN Heterostructures*

We have confirmed the $k$-dependent spin splitting in wurtzite Al$_{x}$Ga$_{1-x}$N/GaN heterostructures. Anomalous beating pattern in Shubnikov-de Haas measurements arises from the interference of Rashba and Dresselhaus spin-orbit interactions. The dominant mechanism for the $k$-dependent spin splitting at high value k is attributed to Dresselhaus term which is enhanced by the $\Delta _{C1}-\Delta _{C3}$ coupling of wurtzite band folding effect.