  In this paper we look at a sigma model based on the (4, 4) twisted chiral
multiplet [3]. It admits two geometric descriptions: The ususal bi-quaternionic
geometry on the tangent space and a new geometry involving two Yano
F-structures on a doubled tangent space. This analysis sheds light on the
recent discussion of semichiral models in [1] and on an upcoming discussion of
complex linears.
