  We explore the situation where all companion $n \times n$ matrices over a
field $F$ are weakly periodic of index of nilpotence $2$ and prove that this
can be happen uniquely when $F$ is a countable field of positive
characteristic, which is an algebraic extension of its minimal simple (finite)
subfield, with all subfields of order greater than $n$. In particular, in the
commuting case, we show even that $F$ is a finite field of order greater than
$n$. Our obtained results somewhat generalize those obtained by Breaz-Modoi in
Lin. Algebra & Appl. (2016).
