@classmethod
def monoclinic(cls, a, b, c, beta, lattice_type='P'):
    """Factory for hexagonal lattices

        :param a: unit cell length
        :param b: unit cell length
        :param c: unit cell length
        :param beta: unit cell angle
        """
    self = cls(float(a), float(b), float(c), 90, float(beta), 90,
        lattice_type=lattice_type, lattice='monoclinic')
    return self
