  Metasurface has recently emerged as a powerful platform to engineer wave
packets of free electron radiation at the mesoscale. Here, we propose that
accelerating waves can be generated when moving electrons interact with an
array of bianisotropic meta-atoms. By changing the intrinsic coupling strength,
we show full amplitude coverage and 0-to-{\pi} phase switching of Smith-Purcell
radiation from bianistropic meta-atoms. This unusual property leads to the
creation of Airy beams that shifts along a parabolic trajectory during
propagation. Experimental implementation displays that evanescent fields
bounded at slotted waveguides can be coupled into accelerating waves via
Smith-Purcell radiation from a designer bianisotropic metasuface. Our results
offer an alternative route towards free electron lasers with diffraction-free,
self-accelerating, and self-healing beam properties.
