We introduce the multiset partition algebra, ${ \rm M\!P}_{ r,k}(x)$, that has bases elements indexed by multiset partitions, where $x$ is an indeterminate and $r$ and $k$ are non-negative integers. This algebra can be realized as a diagram algebra that generalizes the partition algebra. When $x$ is an integer greater or equal to $2r$, we show that ${ \rm M\!P}_{ r,k}(x)$ is isomorphic to a centralizer algebra of the symmetric group, $S_n$, acting on the polynomial ring on the variables $x_{ ij}$, $1\leq i \leq n$ and $1\leq j\leq k$. We describe the representations of ${ \rm M\!P}_{ r,k}(x)$, branching rule and restriction of its representations in the case that $x$ is an integer greater or equal to $2r$.
Categories: math.CO