  Structural and magnetic chiralities are found to coexist in a small group of
materials in which they produce intriguing phenomenologies such as the recently
discovered skyrmion phases. Here, we describe a previously unknown
manifestation of this interplay in MnSb2O6, a trigonal oxide with a chiral
crystal structure. Unlike all other known cases, the MnSb2O6 magnetic structure
is based on co-rotating cycloids rather than helices. The coupling to the
structural chirality is provided by a magnetic axial vector, related to the
so-called vector chirality. We show that this unique arrangement is the
magnetic ground state of the symmetric-exchange Hamiltonian, based on ab-initio
theoretical calculations of the Heisenberg exchange interactions, and is
stabilised by out-of-plane anisotropy. MnSb2O6 is predicted to be multiferroic
with a unique ferroelectric switching mechanism.
