In this paper, we prove that an Hermitian modular form with small weight over the quadratic field with class number one is a linear combination of theta series associated with Hermitian quadratic forms.
"On Hermitian modular forms of small weight over imaginary quadratic fields." Kodai Math. J. 36 (1) 50 - 55, March 2013. https://doi.org/10.2996/kmj/1364562717