Altermagnetism is a magnetic phase with highly anisotropic spin-splitting of particular symmetries but zero net magnetization and offers a promising platform for exploring unconventional superconductivity. I will talk about Cooper pairing in an altermagnetic metal in proximity to conventional s-wave superconductors. I will show that the Cooper pairs induced in the altermagnet acquire a finite momentum, despite the zero net magnetization in the system. Such Cooper-pair momentum is strongly dependent on the direction of Cooper-pair propagation and exhibits unusual symmetric patterns. It gives rise to oscillations of the order parameter with the doping in the altermagnet and/or with the distance from the superconductor, which depend on the junction orientation. These manifest as 0-π transitions in planar Josephson junctions as a function of doping, junction length or orientation. Furthermore, in junctions parallel to the crystalline axis, the superconducting transport is dominated by Cooper pairs moving at large oblique angles away from the junction direction, an effect not seen in ferromagnetic or antiferromagnetic systems.