  We report detailed thermodynamic studies on high-quality single crystals of
the centrosymmetric skyrmion-hosting intermetallic Gd2PdSi3 by means of
high-resolution capacitance dilatometry in fields up to 15 T which are
complemented by specific heat and magnetization studies. Our dilatometric
measurements show magnetoelastic effects associated with antiferromagnetic
order at TN1 = 22.3 K and TN2 = 19.7 K, as well as strong field effects in an
applied magnetic field of 15 Tup to 200 K (150 K) for B||c (B||a*, i.e. B perp
c). The data allow us to complete the magneticphase diagram, including a new
feature at T* approx 12 K below which a new degree of freedom becomesrelevant.
For the first time, the magnetic B vs. T phase diagram for the a*-axis is also
reported. Gr\"uneisen analysis shows the onset of magnetic contributions around
60 K, i.e., well above TN1. Uniaxial pressure dependencies of opposite sign,
-1.3 K/GPa and 0.3 K/GPa, are extracted for the out-of-plane and in-plane
directions at TN1. For T* we obtain dT*/dpc= 1.4 K/GPa. In particular we
elucidate thermodynamic properties of the recently discovered skyrmion lattice
phase and show that it is strongly enhanced by uniaxial pressure.
