There are two possibilities to explore the longevity of the singlet order in 15 N2-ABZ: (1) directly hyperpolarize SO at ULF (protocol 2 in Figure ), and (2) hyperpolarize the net magnetization of ABZ at ultra-low field and transform it into SO at high field with an appropriate magnetization to singlet order conversion pulse sequence (M2S) (protocol 3 in Figure ). Direct hyperpolarization of SO in cis-15 N2-ABZ by performing SABRE at near zero field was demonstrated previously in our work, but in this case SO showed no signs of an extended lifetime. Following this approach, we conducted photo-SABRE experiment while setting ULF field to 0±10 nT, which is close to the maximum of the detected SO field dependence at zero field (see SI). Subsequently, we transferred the sample to the 9.4 T magnet of NMR spectrometer for N signal detection and applied two continuous wave (CW) spin-locking RF-fields simultaneously on the 1 H and 15 N channels.