  We study the effect of large-scale tidal fields on internal halo properties
using a set of N-body simulations. We measure significant cross-correlations
between large-scale tidal fields and several non-scalar halo properties:
shapes, velocity dispersion, and angular momentum. Selection effects that
couple to these non-scalar halo properties can produce anisotropic clustering
even in real-space. We investigate the size of this effect and show that it can
produce a non-zero quadrupole similar in size to the one generated by linear
redshift-space distortions (RSD). Finally, we investigate the clustering
properties of halos identified in redshift-space and find enormous deviations
from the standard linear RSD model, again caused by anisotropic assembly bias.
These effects could contaminate the values of cosmological parameters inferred
from the observed redshift-space clustering of galaxies, groups, or 21cm
emission from atomic hydrogen, if their selection depends on properties
affected by halo assembly bias. We briefly discuss ways in which this effect
can be measured in existing and future large-scale structure surveys.
