  Based on special geometry, we consider corrections to N=2 extremal black-hole
solutions and their entropies originating from higher-order derivative terms in
N=2 supergravity. These corrections are described by a holomorphic function,
and the higher-order black-hole solutions can be expressed in terms of
symplectic Sp(2$n$+2) vectors. We apply the formalism to N=2 type-IIA
Calabi-Yau string compactifications and compare our results to recent related
results in the literature.
