  The ${{^1\mathrm{S}_0}\!-\!{^3\mathrm{P}_0}}$ clock transition in strontium
serves as the foundation for the world's best atomic clocks and for
gravitational wave detector concepts in clock atom interferometry. This
transition is weakly allowed in the fermionic isotope $^{87}$Sr but strongly
forbidden in bosonic isotopes. Here we demonstrate coherent excitation of the
clock transition in bosonic ${}^{88}$Sr using a novel collinear three-photon
process in a weak magnetic field. We observe Rabi oscillations with frequencies
of up to $50~\text{kHz}$ using $\text{W}/\text{cm}^{2}$ laser intensities and
Gauss-level magnetic field amplitudes. The absence of nuclear spin in bosonic
isotopes offers decreased sensitivity to magnetic fields and optical lattice
light shifts, enabling atomic clocks with reduced systematic errors. The
collinear propagation of the laser fields permits the interrogation of
spatially separated atomic ensembles with common laser pulses, a key
requirement for dark matter searches and gravitational wave detection with
next-generation quantum sensors.
