  In this paper, we begin the study of highest weight representations of the
quantized enveloping superalgebra ${\mathfrak U}_q {\mathfrak p}_n$ of type
$P$. We introduce a Drinfeld-Jimbo representation and establish a
triangular-decomposition of ${\mathfrak U}_q {\mathfrak p}_n$. We explain how
to relate modules over ${\mathfrak U}_q {\mathfrak p}_n$ to modules over
${\mathfrak p}_n$, the Lie superalgebra of type $P$, and we prove that the
category of tensor modules over ${\mathfrak U}_q {\mathfrak p}_n$ is not
semisimple.
