[en] During the last two decades the FOPI collaboration has collected a substantial amount of data on heavy-ion collisions at energies available at SIS-18 facility at GSI. Recently, the symmetry energy in the equation of state has been investigated in different collisions systems employing various observables. Different observables have been discussed in the literature which have sensitivity to the symmetry term of the equation of state: In a recent study [1] we systematically investigated charged pion production. The isospin dependences of the π⁺/π^- production ratio was addressed with a comprehensive set of data including 4^0Ca+4^0Ca, 9^6Ru+9^6Ru, 9^6Zr+9^6Zr, and 1^97Au+1^97Au reactions at several energies. The IQMD model [2] has incorporated an intermediate density dependence of the symmetry energy term, this model does not describe our data fully. Comparisons of our data to predictions of the IBUU04 model, reported in [3], support a soft symmetry energy scenario. Subthreshold production of K⁺ and K⁰ was measured in two symmetric systems 9^6Ru+9^6Ru and 9^6Zr+9^6Zr at 1.528 AGeV [4]. A double ratio (K⁺/K⁰)_Ru/(K⁺/K⁰)_Zr obtained from those measurements is found to be consistent with the thermal model prediction. A relativistic mean-field model result using a soft symmetry energy presumption is consistent with our findings, however, only in an infinite nuclear matter approach. In a more realistic microscopic transport calculation the sensitivity to the symmetry energy term is lost although the K⁺/K⁰ ratio is expected to be a sensitive observable. From our findings we do not support this claim at the measured energy and system. In an early FOPI experiment neutron and hydrogen ion measurements have been done using with the large area neutron detector at GSI, LAND. Data obtained in the 1^97Au+1^97Au system at three different energies [5,6] were published. Those data are presently being reanalyzed in order to establish the feasibility a a new experiment measuring the neutron and proton flow at high baryonic density with a high precision. A new experiment has been proposed to systematically study the ratio and the directed flow of neutrons and protons as well as light fragments at GSI. The proposed systems are 1^97Au+1^97Au as well as 9^6Ru+9^6Ru and 9^6Zr+9^6Zr. We expect that with a new experimental setup we are able to constrain the symmetry energy behavior with present state-of-the-art microscopic transport models.(author)