A many-body microscopic band-mixing formulation of variation after projection of angular momentum and conservation of nucleon number is used to study the yrast band and first excitedK π =0+ band in the doubly even nuclei154,156Gd. The computed energy spectra and the interband and intra-band B (E2) values are in good agreement with corresponding experimental data. Connection with the phenomenological model of Stephens and Simon is discussed, bringing out the role played by thei 13/2 neutron pair in the microscopic formalism.