Context :

Aims : In this paper , we aim to measure the strength of the surface magnetic fields for a sample of five intermediate mass T Tauri stars and one low mass T Tauri star from late-F to mid-K spectral types .
While magnetic fields of T Tauri stars at the low mass range have been extensively characterized , our work complements previous studies towards the intermediate mass range ; this complementary study is key to evaluate how magnetic fields evolve during the transition from a convective to a radiative core .

Methods : We studied the Zeeman broadening of magnetically sensitive spectral lines in the H-band spectra obtained with the CRIRES high-resolution near-infrared spectrometer .
These data are modelled using magnetic spectral synthesis and model atmospheres .
Additional constraints on non-magnetic line broadening mechanisms are obtained from modelling molecular lines in the K band or atomic lines in the optical wavelength region .

Results : We detect and measure mean surface magnetic fields for five of the six stars in our sample : CHXR 28 , COUP 107 , V2062 Oph , V1149 Sco , and Par 2441 .
Magnetic field strengths inferred from the most magnetically sensitive diagnostic line range from 0.8 to 1.8 kG .
We also estimate a magnetic field strength of 1.9 kG for COUP 107 from an alternative diagnostic .
The magnetic field on YLW 19 is the weakest in our sample and is marginally detected , with a strength of 0.8 kG .

Conclusions : We populate an uncharted area of the pre-main-sequence HR diagram with mean magnetic field measurements from high-resolution near-infrared spectra .
Our sample of intermediate mass T Tauri stars in general exhibits weaker magnetic fields than their lower mass counterparts .
Our measurements will be used in combination with other spectropolarimetric studies of intermediate mass and lower mass T Tauri stars to provide input into pre-main-sequence stellar evolutionary models .