  In this paper, we define a new metric on Cartan manifolds and obtain a
K\"ahler structure on their cotangent bundles. We prove that on a Cartan
manifold M of negative constant flag curvature, (T* M_0, G, J) has a
K\"aahlerian structure. For Cartan manifolds of positive constant flag
curvature, we show that the tube around the zero section has a K\"aahlerian
structure. Finally by computing the Levi-Civita connection and components of
curvature related to this metric, we show that there is no non- Riemannian
Cartan structure such that (T* M_0, G, J) became a Einstein manifold or locally
symmetric manifold.
