Block sparse matrix with repeated values

[Tim Sears]

I wish to perform the matrix-vector multiplication Ax, where A = (I  
'kron' B), and B is a rectangular matrix.
'kron' is the Kronecker product of two matrices.
Clearly A contains many repeated values. Is there a PETSC format that  
can store this matrix efficiently?
If so how does one populate it?
Cheers,
--Tim