  Above-threshold ionization spectra from cesium are measured as a function of
the carrier-envelope phase (CEP) using laser pulses centered at 3.1 $\mu$m
wavelength. The directional asymmetry in the energy spectra of backscattered
electrons oscillates three times, rather than once, as the CEP is changed from
$0$ to $2\pi$. Using the improved strong-field approximation, we show that the
unusual behavior arises from the interference of few quantum orbits. We discuss
the conditions for observing the high-order CEP dependence, and draw an analogy
with time-domain holography with electron wave packets.
