  The competition between magnetism and Kondo effect is the main effect
determining the phase diagram of heavy fermion systems. It gives rise to a
quantum critical point which governs the low temperature properties of these
materials. However, experimental results made it clear that a fundamental
ingredient is missing in this description, namely superconductivity. In this
paper we make a step forward in the direction of incorporating
superconductivity and study the mutual effects of this phase and
antiferromagnetism in the phase diagram of heavy fermion metals. Our approach
is based on a Ginzburg-Landau theory describing superconductivity and
antiferromagnetism in a metal with quantum corrections taken into account
through an effective potential. The proximity of an antiferromagnetic
instability extends the region of superconductivity in the phase diagram and
drives this transition into a first order one. On the other hand
superconducting quantum fluctuations near a metallic antiferromagnetic quantum
critical point gives rise to a first order transition from a low moment to a
high moment state in the antiferromagnet. Antiferromagnetism and
superconductivity may both collapse at a quantum bicritical point whose
properties we calculate.
