  We deal with $m$-component vector-valued solutions to the Cauchy problem for
linear both homogeneous and nonhomogeneous weakly coupled second order
parabolic system in the layer ${\mathbb R}^{n+1}_T={\mathbb R}^n\times (0, T)$.
We assume that coefficients of the system are real and depending only on $t$,
$n\geq 1$ and $T<\infty$. The homogeneous system is considered with initial
data in $[L^p({\mathbb R}^n)]^m$, $1\leq p \leq \infty $. For the
nonhomogeneous system we suppose that the initial function is equal to zero and
the right-hand side belongs to $[L^p({\mathbb R}^{n+1}_T)]^m\cap [C^\alpha \big
(\overline{{\mathbb R}^{n+1}_T} \big )]^m $, $\alpha \in (0, 1)$. Explicit
formulas for the sharp coefficients in pointwise estimates for solutions of
these problems and their directional derivative are obtained.
