  Using neutrons and x-rays we show the topological kagome antiferromagnet
Mn$_3$Sn for $T<285$~K forms a homogeneous spin and charge ordered state
comprising a longitudinally polarized spin density wave (SDW) with wavevector
$\textbf{k}_{\beta}=k_\beta {\bf \hat{c}}$, a helical modulated version of the
room temperature anti-chiral magnetic order with $\textbf{k}_{\chi}=k_\chi{\bf
\hat{c}}$, and charge density waves with wave vectors $2\textbf{k}_\beta,
2\textbf{k}_\chi$, and $\textbf{k}_\beta+\textbf{k}_\chi$. Though
$\textbf{k}_{\chi}$ and $\textbf{k}_\beta$ coincide for $200~{\rm K}<T<230$~K,
they exhibit distinct continuous $T-$dependencies before locking to
commensurate values of $\textbf{k}_{\beta} = \frac{1}{12}\textbf{c}^{*}$ and
$\textbf{k}_{\chi} = \frac{5}{48}\textbf{c}^{*}$ at low$-T$. Density functional
theory indicates this complex modulated state may be associated with the
nesting of Fermi surfaces from correlated flat kagome bands, which host Weyl
nodes that are annihilated as it forms.
