  Three questions about the intertwining operators for the generalized
principal series on a symmetric R-space are solved : description of the
functional kernel, both in the compact and the non-compact picture, domain of
convergence, meromorphic continuation. A large use is made of the theory of
positive Jordan triple systems. The meromorphic continuation of the
intertwining integral is achieved via a Bernstein-Sato identity, and a precise
description of the poles is obtained.
