  For an irreducible subvariety Z in an algebraic group G we define a
nonnegative integer gdeg(Z) as the degree, in a certain sense, of the Gauss map
of Z. It can be regarded as a substitution for the intersection index of the
conormal bundle to Z with the zero section of T^*G, even though G may be
non-compact. For G a semiabelian variety (in particular, an algebraic torus
(C^*)^n) we prove a Riemann-Roch-type formula for constructible sheaves on G,
which involves our substitutions for the intersection indices. As a corollary,
we get that a perverse sheaf on such a G has nonnegative Euler characteristic,
generalizing a theorem of Loeser-Sabbah.
