  We report on the construction and initial performance studies of two
micromegas detector quadruplets with an area of 0.5 m$^2$. They serve as
prototypes for the planned upgrade project of the ATLAS muon system. Their
design is based on the resistive-strip technology and thus renders the
detectors spark tolerant. Each quadruplet comprises four detection layers with
1024 readout strips and a strip pitch of 415 $\mu$m. In two out of the four
layers the strips are inclined by $\pm$1.5$^{\circ}$ to allow for the
measurement of a second coordinate. We present the detector concept and report
on the experience gained during the detector construction. In addition an
evaluation of the detector performance with cosmic rays and test-beam data is
given.
