We consider the lower semicontinuous functional of the form
$I_f(u)=\int_\Omega f(u){\rm d}x$ where u satisfies a given
conservation law defined by differential operator of degree one
with constant coefficients. We show that under certain constraints
the well known Murat and Tartar's Λ-convexity condition
for the integrand f extends to the new geometric conditions
satisfied on four dimensional symplexes. Similar conditions on
three dimensional symplexes were recently obtained by the second
author. New conditions apply to quasiconvex functions.