PELE (Penetrator with Enhanced Lateral Effectiveness) rounds are a new type of ordnance developed by Rheinmetall in the late nineties and early two thousands.
As the patent shows, they are similar in outward appearance to traditional long-rod penetrators, but are different in cross section:
The basic principle of a PELE is that the outer walls of the penetrator are made of a denser material than the core. At the extremely high velocities that the penetrator strikes the target, density (rather than material strength) is one of the most important factors in determining penetration.