Given a projective variety X over the rational numbers with infinitely
many rational points, it is a natural problem in number theory to count
the number of rational bounds of height less than some bound B. For
special X (namely for X fano), Manin conjectured precise
asymptotics
for this number as B tends to infinity. In this talk we prove Manin's
conjecture for a certain singular del Pezzo surface of degree four, given
as the intersection of two quadrics in five variables.