  We investigate r-process nucleosynthesis in three-dimensional (3D)
general-relativistic magnetohydrodynamic simulations of rapidly rotating
strongly magnetized core collapse. The simulations include a microphysical
finite-temperature equation of state and a leakage scheme that captures the
overall energetics and lepton number exchange due to postbounce neutrino
emission and absorption. We track the composition of the ejected material using
the nuclear reaction network SkyNet. Our results show that the 3D dynamics of
magnetorotational core-collapse supernovae (CCSN) are important for their
nucleosynthetic signature. We find that production of r-process material beyond
the second peak is reduced by a factor of 100 when the magnetorotational jets
produced by the rapidly rotating core undergo a kink instability. Our results
indicate that 3D magnetorotationally powered CCSNe are a robust r-process
source only if they are obtained by the collapse of cores with unrealistically
large precollapse magnetic fields of order $10^{13}$G. Additionally, a
comparison simulation that we restrict to axisymmetry, results in overly
optimistic r-process production for lower magnetic field strengths.
