  We propose a terrestrial detector for gravitational waves with frequencies
between 0.3 Hz and 5 Hz. Therefore, we discuss a symmetric matter-wave
interferometer with a single loop and a folded triple-loop geometry. The latter
eliminates the need for atomic ensembles at femtokelvin energies imposed by the
Sagnac effect in other atom interferometric detectors. It also combines several
advantages of current vertical and horizontal matter wave antennas and enhances
the scalability in order to achieve a peak strain sensitivity of
$2\cdot10^{-21}\,/\sqrt{\mathrm{Hz}}$.
